!  , 


.1*77 


ELEMENTARY  TREATISE 


ELECTRIC  BATTERIES. 


FROM   THE  FRENCH  OP 

ALFRED    J^IAUDET, 


TRANSLATED  BY 

L.    M. 

OF  THE  BELT-  TELEPHONE  CO.  OF  MISSOURI. 


THIRD  EDITION. 


NEW  YORK: 

JOHN    WILEY    &    SONS, 
15  ASTOB  PLACE. 

LIBRAW  OF  THE 

W1YEKSITT  of  GALff OBIU, 


COPYRIGHT,  1880, 
JOHN  WILEY  &  SONS. 


PBEFACE. 


THE  English  translation  of  Mr.  Alfred  Niauclet's  "  La 
Pile  Electrique  "  scarcely  requires  my  commendation  to 
render  it  acceptable  to  the  English-speaking  community 
interested  in  the  subject,  since  the  author's  name  is  so 
well  known  to  electricians. 

This  work  will  serve  to  guide  the  uninitiated  in  the 
choice  and  management  of  batteries,  and  even  the  profes- 
sional electrician  may  find  not  only  new  matter  but  even 
old  material  presented  in  a  new  form,  and  worked  to  new 
developments. 

Telegraphers  generally  will  find  many  of  their  fre- 
quently recurring  problems  solved  in  its  pages,  and  its 
perspicuity  will  save  both  inventor  and  investigator  from 
making  useless  experiments  or  errors,  while  at  the  same 
time  the  work  offers  to  all  new  fields  for  careful  research. 

Although  the  subject  treated  is  so  useful  and  interest- 
ing, yet  this  is,  I  believe,  the  first  time  it  has  received 
such  recognition  in  English  as  its  importance  demands. 

The  translator  was  happily  fitted  for  his  task,  having 
studied  under  the  direction  of  the  author  himself,  and 
with  whose  sanction  he  undertook  his  task. 

GEO.  D'LSTFKEVILLE, 
Electrician,  Western  Union  Telegraph  Co. 

NEW  YORK,  July  23,  1880. 

749495 


PKEFACE  TO  THE  ENGLISH  EDITION. 


The  work  which  we  here  present  to  the  public  is  in  con- 
formity with  the  second  French  edition  of  a  book  the  first 
edition  of  which  appeared  in  1878,  and  which  has  been 
exhausted  in  less  than  two  years. 

~No  other  treatise  upon  the  "Electric  Battery"  has 
hitherto  been  published  either  in  English,  French  or  Ger- 
man. It  has  appeared  desirable  to  meet  this  need,  and  to 
offer  a  complete  guide  to  those  who  wish  to  thoroughly 
study  or  even  to  improve  upon  batteries,  which  are  to-day 
so  extensively  applied  to  different  uses. 

The  order  that  the  author  has  adopted  in  his  exposition 
is  in  some  sense  obligatory.  Single-liquid  batteries  are 
the  first,  historically  and  logically,  to  present  themselves. 
In  connection  with  this  first  part  are  naturally  placed  the 
exposition  of  principles,  definitions  of  terms,  and  the 
study  of  the  phenomenon  of  polarization,  wherein  lies  the 
whole  difficulty  of  the  subject. 

Next  in  order  come  two-liquid  batteries,  in  which  polari- 
zation is  suppressed  or  reduced  according  to  circumstances. 


CONTENTS. 


PAET   FIKST. 

SINGLE-LIQUID  BATTEKIES, 


CHAPTER  I. 

INTRODUCTION. 

PAGE 

Definitions,            .......  1 

Origin  of  the  Name  Pile,       .....  1 

First  Idea  of  the  Battery, 

Properties  of  Amalgamated  Zinc,      ....  7 

Inconstancy  of  Simple  Batteries,            ....  8 

Battery  Cells  joined  in  Intensity,     ....  10 


CHAPTER  II. 

DESCRIPTION  OF   VOLTA'S  BATTERY  AND  ITS  DERIVATIVES. 

Column  Battery,         ......  13 

Volta's  "  Couronne  de  Tasses,"              ....  13 

Cruikshank's  Battery,            .....  14 

Wollaston's  Battery,        .  .  .  .  .  .15 

Spiral  Battery, 17 

Muncke's  Battery,           ......  18 

Sand  Battery,              ......  19 

Nature  of  the  Chemical  Action  in  Volta's  Battery,       .  20 

Action  of  Air  upon  Batteries,            ....  22 


V  CONTENTS. 

CHAPTER  III. 

GENERAL  REMARKS    UPON  BATTERIES. 

PACK 

Ideas  upon  Electric  Resistance,              ....  23 

General  Remarks  upon  Electro-motive  Force  and  Resistance,  24 

Electro-motive  Force,             .....  26 

Measurement  of  Electro-motive  Forces,             ...  31 

Internal  Resistance  of  the  Battery,               ...  32 

Various  ways  of  Joining  Voltaic  Cells,              ...  34 

The  Voltameter,          ......  38 

Secondary  Currents,  Polarized  Electrodes,        ...  41 

Polarization  of  a  Voltaic  Cell,           .            .            .            .  42 

Polarization  in  a  Battery  of  several  Cells,         .           .           .  47 


CHAPTER  IV. 

SULPHURIC-ACID  BATTERIES. 

Batteries  with  Carbon  Electrodes,     ....  49 

Manufacture  of  Carbon  Electrodes,       ....  50 

Use  of  Carbon  Electrodes,      .....  51 

Zinc-Iron  Battery,             ......  53 

Iron-  Copper  Battery,             .....  53 

Other  Combinations,        ......  53 

Smee's  Cell,      .......  54 

Walker's  Platinized  Carbon  Battery,     ....  56 

Tyer's  Battery,            ......  57 

Baron  Ebner's  Battery,    .  ...  .  .58 

Batteries  analogous  to  that  of  Smee,             ...  59 

Remarks  upon  Polarization  in  the  preceding  Batteries,          .  59 


CHAPTER  V. 

ACID  BATTERIES  ANALOGOUS  TO   THAT  OP  VOLTA. 

Hydrochloric-Acid  Batteries,     .....          61 
Nitric-Acid  Batteries,  .  .  .  .  ,  61 

Various  Acid  Batteries,  .....          62 


CONTENTS.  Vll 
CHAPTER  VI. 

BATTERIES   WITHOUT  ACIDS. 

PAGK 

Sea-salt  Batteries,       .           .           .           .                       .  63 

Duchemin's  Electric  Buoy,        .....  64 

Sea-water,  Zinc  and  Copper  Battery,            ...  68 

Zinc,  Iron,  and  Sea- water  Battery,        ....  67 

Accidental  Reversing  of  the  Current,           ...  68 

Chemical  Action  in  Sea-salt  Batteries,  70 

Marine  Batteries,        ......  71 

Sal-Ammoniac  Batteries,            .            .            .  72 

Bagration  Battery,      ......  72 

Carbon-Electrode  Battery,          .....  72 

Action  of  Air  upon  the  preceding  Battery,              .            .  75 

Chemical  Action  in  Sal-Ammoniac  Batteries,               .            .  76 

OTHER   BATTERIES. 

Zinc-Iron-Water  Battery,             .                        .  76 

Iron- Tin  Battery,        ......  77 

Alum  Battery,       ...                        ...  78 

Remarks  upon  Single-Liquid  Batteries,        ...  79 


PART   SECOND. 

Two-LiQuiD  BATTERIES. 


CHAPTER  I. 

THE    DANIELL   BATTERY. 

Introduction,          ......  81 

Description  of  the  Daniell,     .....  88 

Improved  Daniell  Cell,     ......  99 

Balloon  Battery,           .            .            .            .            .            .  101 

A  Reversed  form  of  Daniell's  Battery,  .  .  .102 

Trough  Battery, 104 

Conventional  Figure,       .                        ....  106 


Vlll  CONTENTS. 

PAGE 

Muirhcad's  Battery,     ......  107 

Carre's  Battery,                 108 

Siemens  and  Halske's  Battery,           ....  109 

Varley's  Battery,              ......  110 

Minotto's  Battery,        ......  Ill 

Trouve's  Blotting-Paper  Battery,  .  .  .  .112 

CHAPTER  II. 

GRAVITY   BATTERIES. 

Callaud's  Battery, 118 

Applications  of  Callaud's  Battery,     .            .            .            .  122 

Trouve-Callaud  Battery, 123 

Meidinger's  Battery,                .....  124 

Meidinger's  Flask  Battery,           .....  127 

Kruger's  Battery,        ......  128 

Sir  William  Thomson's  Battery,  .  .  .  .130 

Electro-motive  Force  of  the  Daniell  Gravity  Battery,         .  133 

CHAPTER    III. 

GENERAL  REMARKS  UPON  DANIELL  BATTERIES. 

Amalgamation  of  Zinc  in  the  Daniell,    ....  134 

Copper-Plating,            ......  135 

Irregularity  of  the  Chemical  Action  in  Daniell's  Batteries,      .  137 

CHAPTER  IV. 

BATTERIES  DERIVED  FROM  THE  DANIELL. 

Marie  Davy's  Sulphate-of -Mercury  Battery,      .           .            .  140 

Weakening  of  the  Sulphate-of -Mercury  Battery,                 .  143 

Sulphate-of  Mercury  Gravity  Battery,                .            .           .  146 

Trouve's  Reversible  Battery,              ....  147 

Gaiffe's  Battery,                147 

Latimer  Clark's  Standard  Battery,                .            .            .  148 

Sulphate-of -Lead  Battery,           .....  150 

Weakening  of  the  Sulphate-of -Lead  Battery,          .           .  152 

Various  Salt  Batteries,            .           .           .           .           .  153 


CONTENTS.  IX 

CHAPTER  V. 

ACID     BATTERIES. 

PAdE 

Grove's  Battery,  .  .  .  .  .  .        154 

Chemical  Actions  in  Grove's  Battery,  .  .  .  156 

Bunsen's  Battery,  French  Model,  ....        158 

Bunsen's  Battery,  German  Model,  .  .  .  172 

Bunsen's  Battery,  Faure's  Model,  .  .  .        174 

Electro-motive  Force  and  Resistance  in  Nitric- Acid  Batteries,        174 
Maynooth's  Battery,  .  .  .  .  .  175 

Daniell's  Experiments  upon  the  Size  and  Place  of  the  Elec- 
trodes,         .  .  .  .  .  .  .176 

Chloric- Acid  Battery,  .  .  ,  .  .  177 

Chromic- Acid  Battery,  .  .  .  .  .177 

Various  Acid  Batteries,          .  .  .  .  .  177 


CHAPTER  VI. 

OXIDES  IN  BATTERIES. 

Peroxide-of-Lead  Battery,                 ....  179 

Peroxide-of-Manganese  Battery,              ....  180 

Lcclanche's  Battery,                .....  180 

Leclanche's  Agglomerated  Mixture  Battery,                 .           .  189 

Clark  and  Muirhead's  Modification  of  the  Leclanche,        .  193 

Electro-motive  Force,  Polarization,       ....  194 

Chemical  Action,         .           .           .            .            .            .  194 

Weakening  of  the  Leclanche  Battery,  .  .  .196 

Practical  Durability  of  the  Leclanche  Battery,       .           .  197 


CHAPTER  VII. 

CHLORIDE    BATTERIES. 

Chloride-of -Platinum  Battery,                ....  200 

Chloride-of-Silver  Battery,                 .  201 
Gaiffe's  Battery,                .            .           .           .           .            .206 

Chloride-of -Lead  Battery,       .....  208 

Perchloride-of-Iron  Battery,        .....  208 


X  CONTENTS. 

CHAPTER  VIII. 

DEPOLARIZING-MIXTURE   BATTERIES. 

PAGE 

Potassium-Chlorate  and  Sulphuric- Acid  Batteries,       .            .  210 

Bichromate  of-Potassium  and  Sulphuric- Acid  Batteries    .  211 
Chemical  Action  in  the  Bichromate  Battery,                 .           .213 

Application  to  the  Telegraph,            .            .           .            .  216 

Gaugain's  Experiments,                .....  217 

Use  in  England, 218 

Fuller's  Battery,                218 

Military  Batteries,        ......  220 

Grenet's  Bottle  Battery,               .....  222 

Trouve's  Battery,        ......  224 

Byrne's  Pneumatic  Battery,        .....  226 

Agitation  of  the  Liquid,          .....  228 

Camacho's  Battery,           .           .           .           .                      .  231 

Delaurier's  Battery,                 .....  232 


PAKT   THIRD. 

VARIOUS  BATTERIES. 

Dry  Piles, 235 

Identical  Electrode  Batteries,             .           .           .            .  237 

Unattacked  Electrodes  in  Batteries,        .  .  .  .238 

Becquerel's  Oxygen-Gas  Battery,       ....  239 

Coke-Consuming  Battery,            .....  240 

Gas  Batteries,               ......  242 

Secondary  Batteries,        ......  243 


TABLES. 

Electric  Conductibility  of  Solids,  .  .  .  .253 

Specific  Resistances,  .....  254 

Conductibility  of  Liquids,  .....        255 


CONTENTS.  xi 

PAGE 

Resistances  of  Liquids,            .....  256 

Dilute  Sulphuric  Acid,      ......  257 

Resistance  to  Different  Liquids,            ....  258 

Electro-motive  Forces,            .....  259 

Remarks  upon  the  preceding  tables,       ....  264 

Conclusion,       .           .           .           .           .           .  265 


PART  I, 
SINGLE    LIQUID  BATTERIES. 


OHAPTEE  I. 
INTRODUCTION. 

A  BATTERY,  or  pile  as  it  is  sometimes  called,  is  an  ap- 
paratus arranged  to  furnish  a  continued  flow  of  electricity, 
to  which  the  name  of  "electric  current"  is  given. 

If  one  should  wish  to  make  a  complete  enumeration, 
it  would  be  necessary  to  note  : 

1.  Hydro-electric  batteries,  to  the  study  of  which  the 
present  work  is  devoted ; 

2.  Thermo-electric  batteries,  which  have  as  yet  received 
but  few  applications. 

It  may  be  well  to  state,  however,  that  batteries  are  not 
the  only  apparatus  able  to  produce  currents ;  certain  ma- 
chines produce  effects  exactly  similar. 

OEIGIN   OF  THE  NAME  OF  PILE. 

The  word  pile,  though  not  as  frequently  used  as  the 
word  battery,  is,  however,  more  correct. 

The  invention  of  electric  piles  is  due  to  Yolta,  Profes- 


2  SINGLE  LIQUID   BATTEEIES. 

sor  of  Natural  Philosophy  at  PajVia,  and  dates  from  the 
yea-'  1800. 

One  of  the  first  that  he  constructed  was  composed  of 
a  certain  number  of  discs  made  of  zinc,  copper,  and 
cloth  piled  one  upon  another.  In  all  courses  of  natural 
philosophy  models  of  Velio's  pile  are  shown,  and 


FIG.  1. 

Fig<  1  shows  the  appearance  of  the  instrument  called 
the  column-pile,  which  has  to-day  but  an  historical  in- 
terest ;  it  is  a  pile  of  discs.* 

FIKST  IDEA  OF  THE  PILE, 

OB    BATTERY,   AS    WE    SHALL    HEREAFTER    CALL    IT. 

If  you  immerse  a  thin  plate  of  commercial  zinc  into 

*  This  figure  is  a  fac-simile  of  the  first  cut  published  of  the  bat- 
tery. The  original  cut  is  to  be  found  in  the  "Philosophical  Trans- 
actions" for  1800. 


INTRODUCTION.  3 

dilute  sulphuric  acid,  a  very  lively  action  takes  place ; 
the  zinc  dissolves,  and  a  considerable  quantity  of  hydro- 
gen is  given  off.  It  is  indeed  this  process  which  is  gen- 
erally employed  in  the  preparation  of  hydrogen  gas. 

But  if,  instead  of  ordinary  zinc,  which  contains  im- 
purities, zinc  rendered  perfectly  pure  by  distillation  be 
employed,  the  action  takes  place  very  slowly,  the  bub- 
bles of  hydrogen  remain  attached  to  the  plate  of  zinc  and 
protect  it  from  further  action  of  the  acid. 

If  a  thin  plate  of  platinum,  or  a  platinum  wire,  be 
now  placed  in  the  same,  as  soon  as  the  two  metals  touch 
at  one  point  the  action  becomes  extremely  energetic ;  the 
zinc  dissolves  and  hydrogen  is  given  off,  but  from  the 
platinum  and  no  longer  from  the  zinc. 

As  soon  as  the  contact  of  the  two  metals  ceases,  all  action 
upon  the  zinc  and  all  giving  off  of  hydrogen  are  suspended. 

This  important  experiment,  due  to  De  La  Rive,  throws 
a  great  deal  of  light  upon  all  that  follows.  It  is  equally 
successful  when  you  substitute  for  the  platinum  silver, 
copper,  or  even  iron  ;  it  gives  the  same  result  when  the 
metals  have  their  point  of  contact  either  in  the  liquid  or 
out  of  it. 

It  permits  us  to  explain  the  difference  in  the  action  of 
the  sulphuric  acid  upon  pure  zinc  and  impure  zinc ;  the 
heterogeneous  particles  (of  iron  or  of  other  metals)  found 
at  the  surface  of  commercial  zinc  play  the  same  part  as  the 
platinum.  You  will  observe,  in  effect,  that  the  hydrogen 
is  only  given  off  within  very  limited  points,  and  at  the 
end  of  a  certain  time  the  surface  becomes  rough,  which 
shows  that  the  attack  has  been  more  active  at  some  points 
than  at  others. 

Let  us  resume  the  fundamental  experiment  of  De  La 
Rive. 


4  SINGLE   LIQUID   BATTERIES. 

Suppose  the  two  metals  to  have  their  point  of  contact 
not  in  the  liquid  but  out  of  it,  as  Fig.  2  represents. 
The  chemical  action  takes  place  in  the  liquid,  as  stated 
above. 

It  also  takes  place  if,  instead  of  bringing  the  two  plates 
of  metal  into  direct  contact,  you  put  one  upon  the  up- 
per part  of  the  tongue  and  the  other  upon  the  under  part. 


FIG.  2. 

You  will  experience  a  slight  sensation  like  that  of  a 
feeble  electric  shock,  and  also  a  peculiar  taste. 

If  you  place  upon  the  dry  part  of  the  zinc  a  strip  of 
paper  dipped  in  iodide  of  potassium,  and  then  touch  this 
dampened  paper  with  the  platinum,  a  blue  spot  is  imme- 
diately produced,  which  shows  that  the  iodide  has  been 
decomposed  and  iodine  set  free. 

These  experiments  can  also  be  made  if  you  attach  to 
the  zinc  and  platinum  two  wires  (indeed  very  long  ones 
may  be  used),  and  operate  with  the  two  loose  ends.  If 
you  place  one  of  these  in  the  neighborhood  of  a  freely 
suspended  magnetic  needle,  you  will  notice  that  the 


INTRODUCTION.  5 

needle  deviates  slightly  from  its  north-south  direction  as 
soon  as  the  contact  is  established  between  the  two  loose 
ends  of  the  wires. 

These  different  observations  prove  that  a  singular 
phenomenon  takes  place  in  the  two  wires,  which  is  the 
cause  of  various  actions,  physiological  (upon  the  tongue), 
chemical  (upon  the  iodide  of  potassium),  magnetic  (upon 
the  needle). 

The  analogy  of  these  phenomena  with  those  which 
electric  machines  with  circular  glass  plates  produce,  and 
which  were  known  long  before,  is  easy  to  comprehend. 
It  is  said  that  an  electric  current  runs  over  the  wire,  and 
one  can  see  from  its  effects  that  it  is  continual. 

The  two  metal  plates  immersed  in  the  liquid  (Fig.  3) 


FIG.  3. 


are  called  electrodes  ;  the  wires,  long  or  short,  attached 
to  electrodes,  and  which  permit  the  transference  to  a  dis- 
tance of  the  effects  produced  by  the  battery,  are  called 


6  SINGLE  LIQUID   BATTERIES. 

The  rheophores  are  generally  short,  and  often  end  in  a 
longer  wire,  cccc,  to  which  the  name  of  conductor  is 
given. 

The  name  circuit  of  the  current  is  applied  to  the 
whole,  formed  by  the  battery,  the  rheophores,  and  the 
solid  or  liquid  conductor  through  which  the  current 
passes.  In  the  experiments  mentioned  above,  the  tongue 
and  the  paper  dipped  in  iodide  of  potassium  formed  part 
of  the  circuit. 

Every  apparatus  which  produces  a  current  is  indeed  a 
battery.  However,  the  simple  apparatus  mentioned  above 
(Fig.  3)  is,  to  be  more  exact,  a  cell,  or  an  element,  of  a 
battery,  and  a  number  of  these  cells  grouped  together  is 
properly  a  battery. 

It  is  said  that  the  circuit  is  open  when  at  any  point 
whatever  the  conductor  be  disconnected ;  all  the  effects 
of  the  current  then  cease  and  the  current  does  not  circu- 
late. The  current  is  closed  when  the  two  parts  of  the 
conductor,  which  were  separated,  are  brought  into  con- 
tact with  each  other  and  the  current  commences  to  flow. 

It  is  said  that  a  battery  is  in  short  circuit  when  the 
conductor  connecting  its  poles  has  a  null  resistance  ;  that 
is,  when  it  is  very  short.  We  will  frequently  have  occa- 
sion to  use  this  expression  in  the  course  of  the  present 
work. 

It  has  thus  come  to  be  said  that,  in  the  conductor,  the 
current  flows  from  the  positive  pole  of  the  ~battery  (+plate 
of  copper)  to  the  negative  pole  (-plate  of  zinc) ;  a  transfer- 
ence of  a  peculiar  fluid  from  one  to  the  other  of  these 
points  is  thus  implicitly  admitted.  Let  us  say,  in  pass- 
ing, that  this  way  of  looking  at  things,  after  having  been 
abandoned  in  science,  shows  a  tendency  towards  reaccept- 
ance  with  a  few  changes,  so  that  the  conventional  Ian- 


INTRODUCTION.  7 

guage,  which  had  not  been  changed,  finds  itself  again  in 
accordance  with  the  theoretical  ideas  admitted. 

The  cell  formed  of  the  electrodes  of  zinc  and  copper 
immersed  in  sulphuric  acid  is  more  particularly  known 
under  the  name  of  Yolta ;  by  changing  the  nature  of  the 
liquid  and  the  electrodes,  you  can  obtain  an  indefinite 
number  of  cells  which  produce  the  same  kind  of  energy. 


PKOPEKTIES  OF  AMALGAMATED  ZINC. 

We  have  shown,  in  that  which  precedes,  how  differ- 
ently the  pure  zinc  arid  the  ordinary  commercial  zinc  act 
in  the  voltaic  cells. 

The  result  is  that  when  pure  zinc  is  employed  there 
is  no  local  current  at  its  surface,  and  that  the  electricity 
which  is  produced  passes  entirely  into  the  circuit  be- 
tween the  poles,  and  also  that  the  hydrogen  is  given  off 
from  the  copper. 

If,  on  the  other  hand,  impure  or  commercial  zinc  be 
employed,  the  giving  off  of  hydrogen  takes  place,  for  the 
most  part,  upon  its  surface ;  there  is  reason  to  conclude, 
from  this,  that  a  very  large  proportion  of  the  chemical 
action  is  lost  for  the  production  of  the  electric  current. 

Thus,  in  the  construction  of  batteries,  the  use  of  pure 
zinc  presents  very  important  advantages ;  but  the  price 
of  this  material  is  almost  fabulous,  and  it  can  almost  be 
called  a  curiosity  of  the  laboratory. 

Happily,  a  very  simple  artifice  has  been  discovered,  by 
which  the  properties  of  pure  zinc  may  be  given  to  com- 
mercial zinc.  It  suffices  to  amalgamate  it—that  is,  to 
spread  mercury  over  its  surface  in  such  a  manner  as  to 
form  a  layer  of  amalgam  of  zinc.  This  amalgam  is  an 


8  SINGLE   LIQUID   BATTERIES. 

alloy,  or,  in  other  words,  a  combination  of  zinc  and  mer- 
cury. 

The  experiment  shows  that  the  amalgamated  zinc  im- 
mersed in  sulphuric  acid  diluted  with  water,  is  scarcely 
attacked,  and  if  it  be  employed  as  the  positive  electrode 
of  a  voltaic  cell,  it  occasions  no  local  actions ;  the  giving 
off  of  hydrogen  takes  place  entirely  upon  the  negative 
electrode,  of  copper  or  platinum. 

In  short,  amalgamated  zinc  presents,  for  use  in  bat- 
teries, the  same  advantages  as  the  chemically  pure  zinc, 
and  with  a  few  exceptions  zinc  should  always  be  amalga- 
mated. 

INCONSTANCY  OF  SIMPLE  BATTEEIES. 

All  the  cells  of  which  we  have  spoken,  formed  of  two 
electrodes  immersed  in  a  liquid,  present  an  immense 
drawback ;  namely,  their  action  decreases  very  rapidly 
from  the  beginning  of  the  action. 

The  causes  of  this  decrease  are  twofold,  which  we  will 
analyze  summarily  here. 

The  first  is  the  loss  of  acid  from  the  dilution.  It  can 
be  easily  understood  that  water  acidulated  in  the  propor- 
tion of  1  to  100  will  act  less  energetically  than  water 
acidulated  in  the  proportion  of  1  to  10.  This  cause  of 
the  weakening  of  the  battery  is  not  felt  until  the  expira- 
tion of  a  certain  time,  and  it  is  easily  avoided  by  adding, 
from  time  to  time,  acid  to  the  dilution. 

The  second  is  the  deposit  of  hydrogen  upon  the  cop- 
per. If  the  current  be  interrupted  during  a  length  of 
time  sufficient  for  the  freeing  of  the  hydrogen,  it  will  be 
seen,  as  soon  as  the  current  is  again  closed,  that  the  in- 
tensity assumes  its  original  worth  ;  it  suffices  indeed  to 


INTRODUCTION.  9 

\ 

agitate  the  plate  of  copper  in  order  to  cause  the  gas  to 
free  itself  and  to  give  to  the  current  its  initial  intensity. 

Constant  batteries  are  those  in  which  this  second  cause 
of  weakening,  called  polarization  of  the  electrode,  is  re- 
moved. The  presence  of  the  hydrogen  upon  the  elec- 
trode opposes  a  double  resistance  to  the  passage  of  the 
current,  a  passive  resistance  and  an  active  resistance  • 
it  is  the  latter  that  is  properly  called  polarization  of  the 
electrode.  To  depolarize  the  electrode,  is  to  provide 
against  these  resistances  by  suppressing  the  freeing  of 
hydrogen. 

It  is  very  important  to  comprehend  perfectly  every- 
thing pertaining  to  this  question ;  therein  lies  the  whole 
difficulty  concerning  the  improvement  and  perfecting  of 
batteries.  "We  will  return  to  it  in  the  course  of  our  ex- 
position. 

Various  reasons  have  combined  to  designate  the  posi- 
tive electrode  as  that  one  which  represents  the  negative 
pole  of  the  cell  (zinc,  in  Yolta's  battery),  and  negative 
electrode  as  that  one  which  represents  the  positive  pole 
(copper  or  platinum,  in  the  cells  which  have  occupied  us 
up  to  the  present). 

One  of  these  reasons  has  been  indicated  above,  which 
is  that  the  current  enters  the  liquid  of  the  battery  by  the 
negative  pole,  and  goes  out  by  the  positive ;  in  other 
words,  the  positive  electrode  is  that  by  which  the  elec- 
tricity enters  the  cell. 

However  excellent  may  be  this  reason  and  those  which 
we  will  give  further  on  for  the  choice  of  these  denomi- 
nations, it  is  not  to  be  denied  that  they  are  difficult  to 
employ.  In  reality,  this  difficulty  may  be  avoided  by 
speaking  of  the  positive  pole  and  negative  pole,  when 
you  want  to  designate  the  corresponding  electrodes  ;  that 


10  SINGLE-LIQUID   BATTElilES. 

is  what  the  majority  of  practical  men  do.  But  if  you 
wish  to  employ  absolutely  correct  and  scientific  terms, 
take  great  care  not  to  apply  them  wrongly,  as  you  will 
only  arrive  at  confusion  by  an  awkward  research  for  pre- 
cision in  the  language. 

"We  find  in  the  excellent  book,  "  Darnell's  Introduction 
to  Chemical  Philosophy,"  another  denomination  which 
ought  to  be  employed  more  frequently  than  it  is,  because 
it  presents  the  expression  of  a  fact  and  does  not  depend 
upon  theoretical  ideas,  which  are  always  open  to  discus- 
sion. 

He  calls  the  generating  electrode  that  one  which  plays 
a  part  in  the  chemical  action ;  it  i&  the  zinc  in  the  cell 
that  we  have  considered. 

He  calls  the  conducting  electrode  that  one  which  is  not 
attacked,  and  which  serves,  however,  to  complete  the  cell. 

The  first  can  also  be  called  soluble  electrode. 


BATTERY  CELLS  JOINED  IN  INTENSITY. 

We  have  described  above  the  most  simple  cell  that  can 
be  prepared,  composed  of  two  electrodes  of  copper  and 
zinc  immersed  in  acidulated  water. 

The  cell  of  Yolta's  column-battery  does  not  differ  es- 
sentially from  this  one ;  it  is  composed  of  two  discs,  one 
of  copper  and  the  other  of  zinc,  separated  by  a  circular 
piece  of  cloth  saturated  with  acidulated  water. 

Two  "  rheophores,"  or  copper  wires,  are  soldered  to 
these  two  discs  and  conduct  the  current  to  apparatus 
upon  which  it  is  to  act. 

But  as  we  have  summarily  indicated  from  the  com- 
mencement, Yolta  placed  upon  this  first  group  of  three 
discs  (zinc,  wet  cloth,  copper)  a  second  group  entirely 


INTRODUCTION.  11 

identical  and  disposed  in  the  same  order ;  then  a  third,  a 
fourth,  and  so  on. 

These  discs,  in  various  quantities,  the  one  at  the  top 
being  of  copper  and  the  one  at  the  bottom  of  zinc,  con- 
stitute the  battery  of  Yolta. 

Yolta  discovered,  by  delicate  means,  that  the  force  of 
the  current  increased  as  the  number  of  cells  was  aug- 
mented, and  made  one  of  the  most  brilliant  inventions  of 
modern  times. 

He  thus  showed  that  it  was  possible  to  add  one  source 
of  electricity  to  another  and  to  a  third  in  such  a  manner 
as  to  obtain  a  multiple  source  of  an  indefinitely  increas- 
ing power. 

Although  three  quarters  of  a  century  have  passed  since 
this  discovery,  it  is  not  certain  whether  all  of  its  resources 
have  been  exhausted,  and  it  is  probable  that  unlooked-for 
consequences  may  yet  be  brought  to  light. 

It  is  remarkable  that  he  made  at  the  same  time  an 
invention  and  a  discovery ;  he  invented  an  apparatus,  a 
machine,  an  implement,  which  has  received  and  will  re- 
ceive many  applications :  at  the  same  time  he  discovered 
one  of  the  most  fruitful  principles  of  physics,  to  which 
he  opened  a  new  road. 

If  you  should  wish  to  show  the  increase  of  force  of  a 
battery  with  the  number  of  cells  or  groups  of  three  discs, 
the  most  simple  means  consists  in  causing  the  current  to 
act  upon  a  galvanometer  or  detector.  The  deflection  of 
the  galvanometric  needle  would  be  seen  to  increase  in 
proportion  to  the  number  of  cells ;  that  is  indeed  a  funda- 
mental truth,  verified  by  experiments  at  every  moment. 

The  copper  electrode  of  the  cell  of  Volta  (Fig.  3)  is  the 
positive  pole,  the  zinc  electrode  is  the  negative  pole  of 
the  cell. 


12  SINGLE-LIQUID   BATTERIES. 

When  the  cells  are  piled  up  or  joined  in  intensity  as 
in  Yolta's  battery,  the  positive  pole  of  the  battery  is  that 
of  the  last  cell,  and  the  negative  pole  is  that  of  the  first 
cell. 

In  order  to  give  an  exact  definition  of  the  positive  pole 
of  a  battery,  or  of  a  cell  of  a  battery,  it  is  necessary  to 
say  that  it  is  that  one  whence  the  current  starts  circu- 
lating in  the  exterior  conductor,  and  that  the  negative 
pole  is  that  one  towards  which  this  same  current  flows,  as 
shown  by  the  arrows,  Fig.  3. 

To  be  complete,  it  must  be  added  how  the  direction 
of  the  current  may  be  recognized.  The  wire  through 
which  the  current  flows  being  placed  directly  over  a 
freely  suspended  magnetized  needle,  causes  the  north 
pole  of  the  needle  to  deflect  towards  the  west,  when  the 
current  flows  from  south  to  north. 

These  preliminaries  being  established,  we  may  enter 
upon  the  description  of  the  principal  arrangements  of 
Yolta's  Battery. 


CHAPTER  II. 
THE  VOLTAIC  BATTERY  AND  ITS  DERIVATIVES. 


COLUMN  BATTEEY. 

WE  have  described  this  battery  in  the  preceding 
pages.  We  add  that  it  may  be  vastly  improved  upon  by 
soldering  the  disc  of  copper  of  each  cell  to  the  disc  of 
zinc  of  the  following  cell;  all  faulty  contacts  of  the 
metal  plates  are  thus  avoided. 

The  discs  of  cloth  should  be  smaller  than  the  metal 
discs.  It  is  noticed,  however,  after  a  short  time  that  the 
weight  of  this  column  squeezes  out  the  liquid  from  the 
cloth ;  this  liquid  runs  out  over  the  edges  of  the  discs 
and  soon  disappears,  so  that  the  battery  rapidly  weakens, 
and  after  a  certain  time  produces  no  effect  whatever. 

YOLTA'S  "COUKONKE  BE  TASSES." 

It  is  generally  admitted  that  the  column  battery  was 
the  first  one  that  Yolta  arranged.  This  is,  however,  not 
correct ;  the  "  couronne  de  tasses"  was  the  first ;  and 
according  to  us  is  much  preferable.  A  series  of  glasses 
or  cups  were  placed  in  a  circle,  forming  a  kind  of  a 
crown ;  plates  of  copper  and  zinc  were  so  arranged  that, 
being  connected  at  the  top,  the  plate  of  zinc  was  placed 
in  one  cup  and  the  plate  of  copper  in  the  next. 

This  battery  is  truly  the  model  of  all  those  existing 


14  SINGLE-LIQUID   BATTERIES. 

to-day,  and  will  be  our  model  for  reference  in  the  descrip- 
tion of  others. 

It  is  interesting  to  note  that  Yolta  did  not  think  of  the 
column-battery  until  afterwards,  and  then  it  was  with  a 
view  to  produce  an  instrument  that  might  be  easily  trans- 
ported into  hospitals  for  medical  purposes. 


FIG.  4. 

CEUIKSHANK'S  BATTEKY. 

This  battery  is  composed  of  a  wooden  trough,  inter- 
nally coated  with  marine  glue  and  divided  into  cells 
separated  by  metallic  partitions  ;  these  partitions  are 
composed  of  two  thin  plates,  one  of  zinc  and  the  other 
of  copper,  soldered  together.  They  are  arranged  in  such 
a  manner  as  to  have  all  the  plates  of  zinc  on  the  same 
side  and  all  the  plates  of  copper  on  the  other.  The  cells 
thus  disposed  in  the  wooden  trough  are  nearly  filled  with 
acidulated  water,  and  if  they  are  water-tight  the  battery 
thus  constructed  is  very  satisfactory. 

It  is  not  necessary  to  enumerate  the  inconveniences  of 
Cruikshank's  battery,  which  is  no  longer  in  use ;  we 
would  only  point  out  the  impossibility  of  changing  the 
plates  of  zinc  when  they  have  been  partially  destroyed 
by  the  action  of  the  acid. 


THE  VOLTAIC  BATTERY  AND  ITS  DERIVATIVES.     15 


WOLLASTON'S  BATTEKY. 

The  difficulty  mentioned  above  is  not  to  be  found  in 
the  battery  combined  by  Wollaston. 

The  pairs  of  metallic  plates  (zinc  and  copper)  are  at- 
tached to  a  cross-bar  of  wood,  which  allows  them  to  be 


FIG.  5. 

lifted  out  or  immersed  all  at  the  same  time  in  the  glass 
vessels. 

This  arrangement  is  excellent,  and  is  still  employed 
very  frequently. 

Wollaston  made  another  change  in  the  combinations 
adopted  before  his  time :  he  placed  the  plate  of  zinc  in 
the  centre  and  surrounded  it  with  a  thin  sheet  of  copper, 
thus  giving  to  the  negative  element  a  surface  double  that 
of  the  zinc.  The  reasons  of  this  disposition  are  several, 
upon  which  we  will  remark : 

1.  When  two    plates  are   immersed  in  a  liquid,  the 


16 


SINGLE-LIQUID    BATTERIES. 


two  sides  facing  each  other  alone  combine  in  producing 
the  current ;  the  other  sides  could  be  covered  with  an 
insulating  coating  without  notably  diminishing  the  cur- 
rent. In  Wollaston's  disposition,  the  two  sides  of  the 
zinc  become  active. 

To  this  it  might  be  opposed  that  an  inverse  disposition 
would  present  the  same  advantages,  and  that  a  plate  of 
copper  might  be  placed  between  the  two  plates  of  zinc 


FIG.  5    . 


FIG.  5    . 


so  as  to  make  use  of  the  two  sides  of  the  copper  and  only 
the  half  of  the  surface  of  the  zinc.  But  as  the  zinc  is 
subject  to  local  action  or  waste,  its  size  should  be  reduced 
to  just  that  amount  which  is  requisite  to  maintain  the 
current  required.  There  is,  on  the  other  hand,  no  dis- 
advantage whatever  in  increasing  the  immerged  surface 
of  the  copper,  as  this  metal  is  not  attacked  by  the  dilute 
sulphuric  acid. 

There  is,  we  repeat,  an  advantage  in  reducing  the  sur- 
face of  the  zinc  as  much  as  possible ;  for  when  the  battery 
is  not  in  use  and  the  electrodes,  however,  remain  immerged 
in  the  liquid,  the  attack  upon  the  zinc  continues,  although 


THE  VOLTAIC  BATTERY  AND  ITS  DERIVATIVES.     17 

with  less  intensity,  and  this  dissolving  of  the  sine  is  pure 
loss.  As  this  waste  is  evidently  in  proportion  to  the 
immerged  surface,  it  is  best  to  have  the  least  possible 
surface  of  zinc ;  or  better,  to  have  no  part  of  that  sur- 
face which  may  be  useless  for  the  producing  of  the  cur- 
rent. 

2.  We  have  stated  above  that  hydrogen  is  given  off 
from  the  positive  electrode,  and  that  this  polarization  of 
the  electrode  was  a  cause  of  weakening  of  the  current  of 
the  battery. 

If  the  hydrogen  would  free  itself  as  it  is  generated,  the 
production  of  the  electricity  would  not  be  perceptibly 
diminished ;  but  it  does  not  free  itself — that  is,  not  wholly — 
and  what  remains,  tends  to  reduce  considerably  the  inten- 
sity of  the  current.  It  is  evident  that  the  smaller  the 
surface  the  more  rapidly  a  certain  quantity  of  hydrogen, 
being  produced  upon  the  positive  electrode,  will  act ;  in 
other  words,  the  larger  the  surface  to  be  polarized,  the 
more  slowly  the  effect  of  the  polarization  will  be  felt. 

This  is  the  second  reason  given  for  the  disposition  o.f 
Wollaston,  in  which  the  surface  of  the  zinc  is  entirely 
surrounded  by  the  surface  of  the  copper.  We  will  re- 
turn to  this  subject  farther  on,  in  speaking  of  the  action 
of  the  air  upon  batteries. 

SPIRAL  BATTERY. 

The  two  electrodes  of  this  battery  are  rolled  parallel  to 
each  other  in  the  form  of  a  helix,  and  separated  by  a 
tissue  of  osier ;  in  the  centre  is  a  wooden  handle  to  which 
the  whole  apparatus  is  attached,  and  by  which  it  may  be 
lifted.  It  is  immersed  in  a  bucket  of  acidulated  liquid^ 
and  thus  you  have  electrodes  with  very  large  surfaces 


18  SINGLE-LIQUID  BATTERIES. 

separated  by  a  very  short  distance ;  the  interior  resistance 
of  the  battery  is  consequently  much  reduced,  and  the 
quantity  of  electricity  produced  very  considerable. 

Tin's  battery  presents  some  of  the  advantages  of  that 
of  Wollaston,  inasmuch  as  both  surfaces  of  the  zinc  are 


FIG.  6. 

used  ;  on  the  other  hand,  both  surfaces  of  the  copper  are 
also  used. 

Cells  of  this  description  may  be  joined  in  intensity  as 
those  of  an  ordinary  battery ;  but  they  were  more  fre- 
quently used  separately. 

The  spiral  battery  has  indeed  been  entirely  abandoned 
since  the  inventions  of  Grove,  and  Bunsen  of  Poggen- 
dorff  (with  bichromate  of  potash). 

MUNCKE'S  BATTERY. 

Wollaston's  battery  being  cumbersome  and  unwieldy, 
Muncke,  Young,  the  illustrious  Faraday,  and  others  im- 


THE  VOLTAIC  BATTERY  AND  ITS  DERIVATIVES.     19 

agined  various  ingenious  arrangements  for  joining  a  large 
number  of  cells  in  a  small  volume. 

In  Muncke's  arrangement,  the  parts  where  the  elec- 
trodes of  zinc  and  copper  are  soldered  together  are  placed 
vertically ;  they  are  divided  into  two  series,  the  one  fit- 
ting in  the  other  as  Fig.  Y  represents. 

This  battery,  and  the  one  arranged  by  Faraday,  which 


FIG.  7. 

differs  from  it  very  slightly,  were  employed  for  several 
years  in  laboratories,  as  the  whole  battery  could  be  im- 
merged  in  one  trough,  which  was  very  convenient.  They 
are  completely  put  aside  to-day. 

SAND  BATTEKY. 

This  battery  is  composed  of  a  trough  made  of  teak, 
divided  into  cells  by  partitions  of  slate  or  of  wood ;  to 
make  it  water-tight  it  is  coated  internally  with  marine 
glue.  A  plate  of  amalgamated  zinc  placed  in  one  cell 
is  joined  to  a  plate  of  copper  in  the  adjoining  cell,  and 
resting,  at  their  point  of  contact,  upon  the  partition ;  the 
cells  are  then  filled  with  sand  saturated  with  acidulated 
water. 

This   battery   is   to-day  abandoned,  but   it   presented 


20  SINGLE-LIQUID  BATTERIES. 

many  practical  advantages.  It  was  used  for  a  long  time 
in  the  telegraph  service,  needing  no  attention  for  several 
weeks  at  a  time,  and  was  much  more  easily  moved  from 
one  place  to  *  another,  than  batteries  wherein  the  liquid 
might  be  spilled  when  carried  about. 


NATUKE  OF  THE  CHEMICAL  ACTION  IN 
YOLTA'S  BATTEEY. 

All  the  batteries  that  we  have  just  described  differ 
only  in  their  arrangement  from  that  of  Yolta's ;  in  every 
one  we  find  the  zinc,  the  copper,  and  the  water  acidulated 
with  sulphuric  acid. 

The  chemical  action  is  very  simple.  Under  the  influ- 
ence of  the  water  and  sulphuric  acid,  the  zinc  becomes 
oxydized ;  the  oxide  of  zinc  uniting  with  the  acid  pro- 
duces sulphate  of  zinc,  and  the  hydrogen  of  the  water  is 
given  off  upon  the  electrode  of  copper. 

Thus,  on  one  hand  we  have  the  dissolving  of  a  metal 
(zinc)  in  the  liquid,  and  on  the  other  the  freeing  of  a 
metal  (hydrogen)  which  is  extracted  from  the  liquid  of 
the  battery.  Hydrogen,  although  gaseous,  is  considered 
by  chemists  as  a  metal. 

It  will  be  seen,  as  we  advance,  that  the  action  is  the 
same  in  nearly  all  batteries:  dissolving  of  one  metal, 
freeing  of  another.  On  account  of  its  importance  in 
nature  and  in  chemistry,  hydrogen  will,  of  all  metals 
with  which  we  will  have  to  do,  be  the  one  the  most  fre- 
quently freed  under  the  influence  of  the  battery.  Far 
from  presenting  an  exception  to  the  preceding  rule, 
this  is  a  confirmation  and  a  capital  example. 

All  our  readers  know  that  when  they  prepare  hydro- 


THE  VOLTAIC  BATTERY  AND  ITS  DERIVATIVES.     21 

gen  gas  for  use  in  laboratories,  they  place  small  bits  of 
zinc  in  an  appropriate  jar  with  acidulated  water. 

Since  there  is  an  attack  upon  the  zinc  without  the 
intervention  of  any  other  metal,  it  can  be  seen  that  in 
all  the  forms  of  Yolta's  battery  hydrogen  gas  will  be 
given  off  and  the  zinc  will  be  dissolved  without  closing 
the  circuit ;  that  is,  without  the  production  of  electricity 
by  the  battery.  This  is  one  of  the  greatest  faults  -of 
these  batteries ;  they  are  consumed  without  doing  any 
useful  work,  like  a  horse  who  stands  in  the  stable  and 
eats  without  working. 

In  will  be  seen,  in  that  which  follows,  that  nearly  all 
batteries  present  this  same  difficulty ;  there  are,  however, 
a  few  exceptions,  upon  which  we  will  bestow  particular 
attention. 

The  hydrogen  given  off  under  the  chemical  action  of 
the  battery  appears  upon  the  negative  electrode  of  cop- 
per ;  it  is  seen  in  the  form  of  bubbles  which  rise  and 
leave  the  liquid  more  or  less  rapidly.  But  in  addition  to 
these  visible  bubbles,  there  is  a  large  quantity  of  gas 
deposited  upon  the  surface  of  the  electrodes  and  which 
is  not  seen.  This  invisible  layer  of  gas  is  of  great  im- 
portance in  the  study  of  batteries,  and  produces,  as  we 
have  already  stated,  the  polarization  of  the  electrode. 
We  are  thus  brought  again  to  speak  of  this  phenomenon, 
so  important  in  the  study  of  batteries,  and  of  which  it  is 
the  most  delicate  point.  We  have  taken  the  opportunity 
of  showing  how  this  injurious  action  may  be  overcome, 
and  how  to  obtain  a  partial  depolarization. 


22  SINGLE-LIQUID  BATTERIES. 


ACTION  OF  THE  AIE  UPON  BATTEKIES. 

The  air  acts  very  favorably  upon  batteries  on  account 
of  the  oxygen  it  contains. 

At  the  time  of  the  discovery  of  the  battery,  it  was 
noticed  that  ordinary  cells  exposed  to  the  air  absorbed 
the  oxygen,  and  that  the  current  had  a  tendency  to  stop 
when  there  remained  nothing  but  nitrogen.  But  obser- 
vation shows  that  the  effect  is  due,  not  to  the  action  of 
the  oxygen  upon  the  zinc,  but  to  a  depolarization  of  the 
other  electrode.  In  the  cells  of  Volta  and  Wollastou,  the 
action  of  the  oxygen  is  experimentally  demonstrated. 

It  will  be  noticed  that  this  depolarizing  action  is  great- 
er in  Wollaston's  battery,  which  is  a  new  reason  explain- 
ing the  advantages  of  giving  to  the  negative  or  conduct- 
ing electrode  a  considerably  larger  surface  than  that  of  the 
generating  electrode.* 

*  These  remarks  are  only  correct  when  concerning  single-liquid 
batteries.  There  is  no  action  of  air  in  batteries  totally  depolarized, 
like  that  of  Daniell. 


OHAPTEE  III. 
GENERAL  REMARKS  UPON  BATTERIES. 


IDEAS   UPON  ELECTKIC   EESISTANCE. 

WE  have  said  that  the  most  simple  way  of  showing 
the  passage  of  electric  currents  in  a  conducting  body  is 
to  bring  its  force  to  bear  upon  a  magnetic  needle. 

Let  us  suppose  that  the  conductor  of  a  galvanometer, 
or  of  a  simple  detector,  be  inserted  in  the  circuit  of  the 
current  of  a  battery,  and  that  the  deflection  of  the  needle 
be  25°,  for  instance.  Now  if  the  circuit  be  lengthened 
by  the  addition  of  a  wire,  the  deflection  will  be  seen  to 
diminish  to  15°,  and  if  the  circuit  be  made  still  longer, 
the  deflection  of  the  needle  will  not  exceed  10°.  From 
this  experiment  several  conclusions  may  be  drawn  : 

1.  The  intensity  of  the  current  is  less  in  the  second  in- 
stance than  in  the  first,  and  less  in  the  third  than  in  the 
second. 

2.  The  influence  of   the  additional   wire   being  only 
passive,  the  reduction  of  the  intensity  of  the  current  is 
due  not  to  the  decrease  of  the  generating  force,  but  to  the 
increase  of  the  resistance. 

These  experiments  give  an  idea  of  the  resistance  that 
conducting  bodies  offer  to  the  passage  of  currents ;  and 
they  also  demonstrate  that  the  resistance  of  a  conductor 
increases  with  its  length. 

Yery  exact  and  oft-repeated  measurements  have  proved 


24  SINGLE-LIQUID  BATTERIES. 

that  the  resistance  of  a  conductor  is  in  proportion  to  its 
length  and  in  inverse  proportion  to  its  sectional  area. 

We  will  not  dwell  upon  the  demonstration  of  these 
laws,  which  are  found  in  all  works  upon  physics.  It  suf- 
fices for  practical  men  to  know  the  formulae  of  these 
rules  which  are  constantly  being  applied. 

GENERAL   REMARKS  UPON 
ELECTRO-MOTIVE  FORCE  AND  RESISTANCE. 

In  all  machines  in  motion  is  seen  a  power  or  cause  of 
movement;  and  there  are  also  resistances  which  tend 
more  or  less  to  slacken  this  movement  or  to  stop  it  alto- 
gether. Let  us  take,  for  instance,  a  windmill.  The  large 
arms,  under  the  pressure  of  the  wind,  cause  the  mill- 
stones to  turn  which  crush  the  grain.  In  the  working 
of  the  mill  we  see  first  a  power,  the  wind,  which  pro- 
duces the  movement. 

Then  there  is  a  resistance  offered  by  the  grinding; 
this  resistance  moderates  the  pace  of  the  arms,  and  if  the 
wind  falls  it  stops  them  entirely. 

At  first  sight  there  are  two  mechanical  elements  ap- 
parent :  the  power  or  cause  of  movement,  or  motive  force ; 
and  the  resistance,  or  work. 

A  careful  examination  will  show,  however,  that  the 
resistance  is  complex,  and  that  that  offered  by  useful 
work,  as  the  grinding,  should  be  distinguished  from  that 
which  is  the  result  of  the  friction  of  the  different  parts 
of  the  machine  in  motion,  and  of  certain  secondary  phe- 
nomena. All  practical  men  know  that  a  badly  oiled  rub- 
ber is  sufficient  to  slacken  the  movement  of  a  machine, 
or  even  to  stop  it ;  all  know  the  importance  of  friction 
in  the  different  parts  of  the  machine,  and  of  the  stiffness 


GENERAL   REMARKS   UPON   BATTERIES.  25 

of  tlie  belts  and  ropes.  These  inevitable  causes  of  the 
slackening,  which  absorb  a  part  of  the  motive  power  at 
the  cost  of  the  useful  work  desired,  are  called  passive  re- 
sistances. Every  one  knows  that  these  resistances  should 
be  diminished  as  much  as  possible,  and  that  they  cannot 
be  totally  suppressed. 

Attention  should  be  called  to  the  fact  that  in  many 
cases  no  useful  work  is  done,  and  that  there  then  remain 
only  passive  resistances.  If  the  miller  takes  away  his 
millstones  and  still  permits  the  mill  to  turn,  it  is  evident 
that  there  remain  only  those  passive  resistances  (friction 
and  others)  which  are  produced  by  the  machinery  remain- 
ing in  motion.  If  all  the  machines  of  a  large  factory 
be  disconnected  from  the  motion-giving  steam-engine 
and  the  engine  continues  to  turn,  there  will  only  be 
present  the  motive  force  furnished  by  the  engine  itself 
and  the  passive  resistances  existing  in  the  engine,  in  the 
shafts,  and  in  the  different  agents  of -the  transference  of 
the  movement  which  are  still  in  motion.  If  now  the 
steam-engine  runs  entirely  alone,  not  being  connected 
with  any  shaft  or  any  piece  of  machinery  outside  of  it- 
self, we  have  not  only  the  example  of  a  system  in  which 
there  are  force  and  passive  resistances,  but  also  that  par- 
ticular instance  where  these  passive  resistances'  are  inhe- 
rent to  the  force-giving  machine  and  inseparable  from  the 
production  of  that  force. 

In  a  circuit  through  which  an  electric  current  flows, 
the  same  terms  are  to  be  found :  first,  a  force  residing  in 
the  battery  and  which  is  called  electro-motive  force  •  next, 
the  work ;  and  finally  the  passive  resistances.  The  work 
may  be  found  in  the  movement  of  the  clapper-spring  of 
an  electric  bell ;  it  may  be  in  the  movement  of  a  tele- 
graph instrument  placed  at  a  great  distance  from  the 


26  SINGLE-LIQUID  BATTERIES. 

battery ;  it  may  be  in  the  movement  of  an  electro-motor 
or  an  electro-magnetic  machine  which  lifts  a  weight ;  it 
may  be  in  a  chemical  decomposition  produced  by  the 
passage  of  a  current  in  the  production  of  heat  and  con- 
sequently of  light  in  a  voltaic  arc,  etc.  etc. 

Passive  resistances  are  the  results  of  the  circulation  of 
the  current  in  the  different  parts  of  the  circuit.  We 
have  explained  how  their  existence  may  be  ascertained, 
and  we  have  designated  them  by  this  one  word  resistance. 

If  the  current  produces  no  real  work — that  is,  if  the 
circuit  is  composed  solely  of  conductors  without  the 
interposition  of  any  apparatus  which  puts  the  current 
to  any  use — the  resistance  is  entirely  passive.  These  con- 
siderations explain  and  justify  the  use  of  the  word  resist- 
ance applied  to  that  property  of  reducing  the  intensity 
of  the  electric  current  which  the  conductors  possess,  and 
which  we  have  demonstrated  in  the  preceding  chapter. 

ELECTEO-MOTIYE  FORCE. 

The  cause  which  produces  the  electric  current  we 
have  called  electro-motive  force.  Before  going  farther  we 
will  show  several  experiments,  which  will  render  the 
ideas  upon  this  force  more  precise. 

Let  us  take  a  battery  cell  (Fig.  3 — zinc,  copper,  and 
water  acidulated  with  sulphuric  acid)  and  cause  the  cur- 
rent which  it  produces  to  act  upon  a  galvanometer,  and 
we  will  see  that  the  needle  is  deflected,  for  instance, 
towards  the  right.  If  we  change  the  communications 
of  the  battery  with  the  galvanometer,  the  direction  of 
the  needle's  deflection  will  be  altered,  which  shows  that 
the  direction  of  the  current  in  the  galvanometer  has  been 
changed. 


GENERAL   REMARKS   UPON   BATTERIES.  27 

But  let  us  consider  the  first  conditions :  the  needle  is 
deflected  towards  the  right. 

Let  us  now  take  a  second  battery  cell,  differing  in 
no  way  from  the  first,  and  insert  it  in  the  circuit.  If 
the  negative  pole  of  the  second  be  attached  to  the  posi- 
tive pole  of  the  first,  the  two  currents  flow  in  the  same 
direction  and  join  each  other ;  the  intensity  of  the  result- 
ing current  is  increased,  and  consequently  the  deflection 


FIG.  8. 


of  the  needle  is  greater.  In  these  conditions  the  two 
battery  cells  are  joined  in  intensity  (Fig.  8) ;  they  form 
a  battery  of  two  cells.  A  battery  of  any  number  of  cells 
could  thus  be  formed  as  we  have  stated  above,  but  that 
is  not  the  point  upon  which  we  wish  to  insist ;  we  only 
desire  to  recall  the  expression,  battery  cells  joined  in 
intensity,  and  to  determine  its  exact  meaning. 

Suppose  now  that  the  second  cell  be  inserted  in  the 
circuit  of  the  first ;  by  uniting  the  positive  pole  to  the 


28 


SINGLE-LIQUID  BATTERIES. 


positive  pole,  and  the  negative  to  the  negative,  in  such 
a  manner  as  to  have  two  poles  of  the  same  name  ending 
at  the  galvanometer  (Fig.  9),  the  needle  will  remain 
stationary.  This  is  not  to  be  wondered  at,  if  it  be  re- 
membered that  the  two  cells  tend  to  produce  equal  cur- 
rents in  opposite  directions.  It  is  quite  natural  that 
these  currents  balance  each  other,  and  that  there  is  no 
movement  either  in  one  direction  or  the  other.  It  is 


FIG.  9.  " 


said  in  this  case  that  the  two  battery  cells  are  opposed  to 
each  other,  or  are  joined  in  opposition. 

We  have  assumed,  in  the  preceding,  that  the  opposed 
cells  were  of  equal  dimensions.  Each  one  acting  alone 
would  produce  the  same  deflection  of  the  needle,  one  to- 
wards the  right  and  the  other  towards  the  left ;  both  acting 
simultaneously  in  opposite  directions  cause  no  deflection 
whatever:  which  is  quite  natural  and  easily  understood. 

Let  us  now  vary  the  experiment,  and  place   in  the 


GENERAL   REMARKS    UPON    BATTERIES.  29 

same  circuit  (Fig.  10)  a  small  voltaic  cell  in  opposition  to 
a  larger  one  of  the  same  nature ;  the  needle  will  remain 
stationary,  thus  showing  that  there  is  no  current.  This 
result  will  appear  very  strange  to  the  uninitiated  reader, 
and  deserves  to  be  dwelt  upon.  If  they  are  made  to  act 
separately,  they  cause  the  needle  to  deflect,  one  towards 
the  right,  the  other  towards  the  left.  The  current  fur- 
nished by  the  larger  one  is  more  intense  than  the  current 


FIG.  10. 

produced  by  the  smaller  one,  as  the  deflections  of  the 
needle  show.  But  if  these  two  cells  be  opposed  to  each 
other,  the  effect  of  one  is  counterbalanced  by  the  effect 
of  the  other,  and  no  current  flows  through  the  circuit. 
The  conclusion  of  this  capital  experiment  is  that  the 
electro-^rrwtive  force  of  battery  cells  does  not  depend  upon 
their  dimensions. 

The  above  experiment  may  be  slightly  modified.   "When 
cells  of  equal  dimensions  are  opposed  to  each  other,  there 


30 


SINGLE-LIQUID  BATTEEIES. 


is  no  deflection  of  the  galvanometric  needle.  You  may 
lift  up  the  zinc  or  the  copper  of  one  of  the  cells,  or  even 
the  zinc  and  copper  together  of  one  of  the  cells ;  you 
may,  in  a  word,  increase  or  diminish  the  immersed  part 
of  the  electrodes  of  one  of  the  cells,  and  still  there  will 
be  no  deflection  of  the  needle,  and  the  electro-motive 
forces  remain  equal. 

To  elucidate  still  further  this  subject,  we  will  present 
a  few  more  experiments. 


FIG.  11. 

Place  two  cells  in  opposition  to  each  other,  the  one 
similar  to  those  of  which  we  have  spoken  (zinc,  copper, 
and  dilute  sulphuric  acid),  and  the  other  differing  but 
slightly  in  appearance  (iron,  copper,  and  dilute  sulphuric 
acid).  The  difference  is  the  substitution  in  the  second 
of  iron  for  zinc.  A  first  trial  will  show  that  the  copper 
is  the  positive  pole  in  the  second  cell  as  in  the  first ;  that 
is,  the  current  flows  from  the  copj>er  to  the  iron  in  the 


GENERAL   REMARKS   UPON   BATTERIES.  31 

second,  as  it  does  from  the  copper  to  the  zinc  in  the  first. 
Place  them  now  in  the  same  circuit,  in  opposition  to 
each  other — that  is,  join  the  two  zinc  poles  and  connect 
the  other  two  with  the  wires  of  a  galvanometer  (Fig.  11) ; 
the  needle  will  be  seen  to  deflect  in  the  same  direction 
as  if  the  voltaic  cell  were  acting  alone,  although  the 
deflection  is  less.  We  have  a  right  to  conclude  from 
-this  that  the  first  cell  has  a  greater  electro-motive  force 
than  the  second,  and  that  the  substitution  of  iron  for 
zinc  in  Volttfs  battery  would  be  detrimental. 

In  this  experiment  we  have  supposed  the  two  cells  to 
be  of  equal  dimensions,  and  that  the  electrode  of  iron 
was  the  same  size  as  that  of  zinc.  We  can  now  modify 
these  dimensions.  Let  us  suppose,  for  instance,  that  a 
very  small  voltaic  cell  be  placed  in  opposition  to  a  very 
large  cell  (iron,  copper,  and  acid). 

The  direction  of  the  deflection  will  be  the  same  as  in 
the  preceding  experiment ;  that  is,  the  electro-motive 
force  of  the  smaller  cell  is  greater  than  that  of  the  larger 
one.  This  new  experiment  proves  again,  and  more  clear- 
ly than  ever,  that  the  electro-motive  force  of  battery  cells 
does  not  depend  upon  their  dimensions,  but  upon  the  ma- 
terials used  in  their  composition. 


MEASUKEMENT   OF  ELECTKO-MOTIYE 
FORCES. 

It  has  been  seen  how,  by  means  of  an  ordinary  galva- 
nometer, the  electro-motive  forces  of  different  batteries 
may  be  compared.  The  method  that  we  have  used  is 
called  method  of  opposition,  because  it  consists  in  oppos- 
ing equal  or  unequal  forces  to  each  other. 


32  SINGLE-LIQUID  BATTERIES. 

It  can  be  easily  understood  how  the  electro-motive 
forces  of  different  cells  may  thus  be  measured  and  tables 
of  these  forces  made  out. 

Let  us  take  two  batteries,  A  and  B,  of  unequal  electro- 
motive forces.  A  first  experiment  will  show  us,  for  in- 
stance, that  A  io  stronger  than  B.  By  opposing  A  to  2B 
we  find  that  2B  is  stronger  than  A.  Let  us  now  oppose 
2 A  to  3B,  and  if  there  is  no  deflection  of  the  galvano- 
metric  needle  wre  may  conclude  that  twice  the  electro- 
motive force  of  A  is  equal  to  three  times  that  of  B,  or 
that  A  =  |  B,  or,  finally,  that  A  =  1£B. 

It  is  seen  that  this  method  is  general ;  it  may  be  varied 
advantageously  in  different  ways.  We  will  not  insist 
upon  it  any  longer,  as  we  only  wished  to  show  the  possi- 
bilities of  these  measurements  and  not  the  way  to  obtain 
them. 

HSTTEBNAL  KESISTANCE  OF  THE  BATTEEY. 

It  has  been  seen  from  the  foregoing  that  the  conduc- 
tors outside  of  the  battery  offer  a  certain  resistance  to 
the  electric  movement,  or,  in  other  words,  a  resistance  to 
the  passage  of  the  current. 

We  wrill  now  show  by  several  simple  experiments  that 
the  battery  itself  offers  a  resistance  to  the  current  it  pro- 
duces. 

The  elementary  battery  (Fig.  3)  is  made  to  act  upon  a 
galvanometer.  Observe  the  deflection.  Lift  up  gradually 
one  of  the  electrodes,  and  as  the  immersed  surface  be- 
comes less  the  deflection  diminishes. 

The  result  shows  a  decrease  in  the  intensity  of  the  cur- 
rent. As  our  former  experiments  have  shown,  however, 
that  the  electro-motive  force  does  not  vary  under  these 


GENERAL   REMARKS   UPON   BATTERIES.  33 

circumstances,  and  that  the  other  parts  of  the  circuit  do 
not  change,  we  are  justified  in  saying  that  the  resistance 
of  the  battery  has  increased. 

The  result  would  be  the  same  if  the  two  electrodes 
were  lifted  at  the  same  time. 

The  experiment  may  be  made  by  separating  the  two 
electrodes  from  each  other,  still  having  the  same  extent 
of  surface  immersed.  It  is  perhaps  in  this  manner  that 
the  experiment  is  made  the  most  clear.  In  these  experi- 
ments the  intensity  of  the  current  is  seen  to  change  with 
the  distance  that  separates  the  two  electrodes  in  the  trough 
of  liquid  and  with  the  section  of  the  trough.  It  maybe 
concluded  that  batteries  have  an  internal  resistance  in 
themselves,  and  that  the  resistance  increases  with  tlie  dis- 
tance between  the  electrodes  in  the  liquid,  and  diminishes 
when  the  immersed  surfaces  are  increased. 

If  the  battery  be  considered  as  a  force-producing  ma- 
chine, it  is  not  to  be  wondered  at  that  it  at  the  same  time 
produces  force  and  offers  a  resistance  to  that  force.  This 
condition  is  common  to  all  machines ;  a  part  of  the 
force  they  produce  is  absorbed  by  those  passive  resist- 
ances resulting  from  the  action  of  the  different  parts  of 
the  machine.  In  a  steam-engine,  for  instance,  the  fric- 
tion of  the  steam  in  the  pipes,  the  friction  of  the  piston 
in  the  cylinder,  etc.  etc.,  cannot  be  avoided. 

This  resistance  of  the  battery  has  to  be  taken  into  ac- 
count in  nearly  all  cases  for  the  explanation  of  phenome- 
na and  for  the  calculation  of  results. 

It  can  be  seen  that  of  two  batteries  in  which  the  elec- 
trodes are  of  unequal  dimensions,  the  distance  between 
them  being  equal  in  each,  the  one  having  the  larger  elec- 
trodes offers  less  resistance  than  the  other ;  and  it  can  be 
said  in  general  that  large  cells,  when  compared  with  small 


34  SINGLE-LIQUID  BATTERIES. 

ones,  offer  less  resistance,  because  the  increase  of  surface 
of  the  electrodes  is  greater  than  the  increase  of  the  dis- 
tance between  them. 

The  resistance  of  the  batteries  varies  with  the  nature 
of  the  liquids  in  which  the  electrodes  are  immersed.  It 
can  be  easily  understood  that  all  liquids  have  not  the  same 
specific  power  of  resistance.  The  conductivity  of  di- 
lute sulphuric  acid  varies  with  the  proportions  of  water 
and  acid  mixed,  and  the  greatest  conductivity  is  found  in 
a  mixture  of  29  parts  of  sulphuric  acid  (HSO4)  for  71 
parts  of  water.  It  has  been  observed  that  it  is  this  mix- 
ture which,  in  an  apparatus  for  the  production  of  hydro- 
gen, attacks  the  zinc  the  most  energetically. 

These  reasons  would  lead  to  the  use  of  this  mixture  in 
preference  to  all  others  in  Volta's  battery,  and  indeed  in 
all  others  in  which  dilute  sulphuric  acid  is  used ;  but  this 
mixture,  being  that  of  about  one  part  of  acid  (HSO4) 
for  two  parts  of  water,  is  not  used  in  the  practice,  as  it 
would  be  too  dangerous  to  handle,  and  as  it  is  also  rather 
costly ;  therefore  the  mixture  of  ten  or  twelve  parts  of 
acid  for  one  hundred  parts  of  water  is  adopted. 

It  is  understood  that  as  soon  as  a  battery  is  put  into 
working  order  and  the  chemical  action  takes  place,  the 
composition  of  the  liquid  changes,  and  consequently  the 
resistance. 

We  will  return  more  than  once  to  this  important  point. 

VAKIOUS  WAYS  OF  JOINING  VOLTAIC 
CELLS. 

We  have  seen  (Fig.  9)  how  two  battery  cells  of  the 
same  kind  may  be  placed  in  opposition  to  each  other  in 
such  a  manner  as  to  counterbalance  each  other.  Let  us 


GENERAL    REMARKS   UPON    BATTERIES. 


35 


now  take  away  the  galvanometer  that  we  had  placed  in 
the  circuit  of  these  cells  and  we  will  still  have  two  cells 
joined  in  opposition. 

Let  us  consider  the  two  cells  thus  joined.  If  the  gal- 
vanometer be  put  into  communication,  on  one  hand  with 
the  wire  connecting  the  two  positive  poles,  and  on  the 
other  hand  with  the  wires  connecting  the  two  negative 
poles,  the  passage  of  a  very  strong  current  will  be  ob- 
served. The  currents  of  the  two  cells,  which  were  at  first 


FIG.  12. 

opposed  to  each  other,  now  flow  together  in  the  galva- 
nometer. The  two  battery  cells  are  then  said  to  be  joined 
in  quantity. 

The  metallic  piece  which  connects  the  two  zinc  poles 
may  be  considered  as  the  negative  pole  common  to  both 
cells,  and  the  other  as  the  positive  pole  common  to  both 
cells. 

It  may  be  observed  that  the  two  cells  ought  to  pro- 


36 


SINGLE-LIQUID  BATTERIES. 


duce  the  same  effects  as  a  single  one,  in  which  the  elec- 
trodes would  have  a  double  surface,  while  the  distance 
between  them  would  remain  the  same. 

The  internal  resistance  offered  bj  the  two  cells  is  only 
half  of  that  offered  by  each  one  alone,  while  the  electro- 
motive force  remains  the  same.  This  may 
be  demonstrated  by  placing  a  third  cell  of 
the  same  size  and  kind  in  opposition  to  these 
two  cells  joined  in  quantity,  Fig.  12.  The 
galvanometric  needle  does  not  deflect,  which 
shows  once  more  that  the  electro-motive  force 
does  not  depend  upon  the  size  of  the  elee 
trodes,  but  solely  upon  their  nature. 

There  is,  finally,  a  third  way  of  joining 
these  two  cells  ;  namely,  joining  them  in  in- 
tensity, of  which  we  have  already  spoken. 
This  manner  consists  in  uniting  the  positive 
pole  of  one  pf  the  cells  to  the  negative  pole 
of  the  other.  In  this  arrangement  the  electro- 
motive force  of  the  two  taken  together  is 
double  that  of  each  separately;  the  resist- 
ance is  also  double. 

These  different  ways   of  joining  battery 
cells  may  be  applied  to  any  number  of  cells. 
^e*  us  ^6,  ^or  instance,  six  cells  and  join 
them  in  intensity,  Fig.  13.     If  the  electro- 
motive force,  of  one   cell  be  symbolized  by  E,  and  its 
resistance  by  K,  it  is  evident  that  a  battery  of  six  cells 
joined  in  intensity  will  have  an  electro-motive  force  equal 
to  6E,  and  a  resistance  equal  to  6E. 
If  all  be  joined  in  quantity,  Fig.  14,  the  electro-motive 

force  of  the  battery  will  be  E,  and  the  resistance  —  - 


FIG  13 


GENERAL    REMARKS    UPON    BATTERIES. 


37 


If  they  be  joined  by  twos  in  intensity  and  by  threes  in 
quantity,  Fig.  15,  the  electro-motive  force  will  be  2E, 
and  the  resistance  f  R. 


FIG.  14. 


They  may,  finally,  be  joined  by  threes  in  intensity  and 
by  twos  in  quantity,  Fig.  16 ;  the  electro-motive  force  will 
be  3E,  and  the  resistance  f  K. 


FIG.  15. 


FIG.  16. 


38  SINGLE-LIQUID  BATTERIES. 

As  long  as,  in  this  last  combination,  there  is  no  con- 
nection with  any  outside  circuit,  the  three  cells  on  the 
right  are  in  opposition  to  the  three  on  the  left.' 

It  is  not  necessary  for  us  to  insist  longer  upon  this 
subject,  or  to  make  calculations  which  are  indeed  very 
simple,  to  make  the  reader  understand  that,  with  a  suf- 
ficient number  of  cells,  a  battery  may  be  obtained  whose 
electro-motive  force  will  be  as  great,  and  whose  resistance 
will  be  as  little,  as  can  be  desired. 

In  most  applications,  and  notably  in  the  electric  tele- 
graph, there  is  only  the  need  of  increasing  the  electro- 
motive force,. and  very  little  attention  is  paid  to  the  re- 
sistance. 

In  certain  instances,  however,  too  great  a  resistance 
would  be  very  detrimental ;  it  is  then  that  the  cells  may 
be  joined  in  quantity.  In  practice,  large  cells  having  a 
very  slight  internal  resistance  are  employed. 

VOLTAMETER 

Before  proceeding  with  the  study  of  batteries,  it  would 
be  well  to  stop  and  examine  some  of  the  effects  they  pro- 
duce. Of  all  the  chemical  actions  that  can  be  brought 
about  by  means  of  electric  currents,  the  decomposition  of 
water  is  the  most  striking.  It  is  done  i-n  an  apparatus 
called  voltameter,  and  is  represented  in  Fig.  IT. 

Two  wires  or  plates  of  platinum,  are  placed  parallel  to 
each  other  in  a  jar  containing  dilute  sulphuric  acid. 
These  two  electrodes  pass  through  the  bottom  of  the 
jar  and  are  attached  to  binding  screws,  or  terminals,  to 
which  the  wires  of  a  battery  are  fastened. 

If  a  sufficiently  energetic  current  be  made  to  pass  in 
this  apparatus,  bubbles  of  gas  will  be  seen  to  free  them- 


GENERAL    REMARKS   UPON   BATTERIES.  39 

selves  from  the  surface  of  the  electrodes.  If  these  gases 
be  collected  in  proper  gas-measuring  jars,  oxygen  will  be 
found  in  one  and  hydrogen  in  the  other.  If  they  be 
collected  together  in  a  single  jar,  they  will  be  found  to 
be  sensibly  in  those  proportions  whose  combination  pro- 
duces water.  We  say  sensibly,  for  the  proportion  is 
nearly  always  altered  by  complicated  disturbing  actions, 
upon  which  we  cannot  here  enlarge. 


FIG.  17. 

The  electrode  by  which  the  current  enters  the  appa- 
ratus is  called  positive  electrode  of  the  voltameter ;  it  is 
that  which  is  connected  with  the  positive  pole,  or,  in 
other  words,  with  the  negative  electrode  of  the  battery 
which  furnishes  the  current. 

The  negative  electrode  of  the  voltameter  is  connected 
with  the  negative  pole,  or  positive  electrode  or  generat- 
ing electrode  of  the  battery. 

The  oxygen  which  appears  upon  the  positive  electrode 
of  the  voltameter  is  termed  electro-negative;  the  hydrogen 
which  is  seen  at  the  surface  of  the  negative  electrode  of 
the  voltameter  is  termed  electro-positive. 

These  denominations  may  embarrass  beginners.  In 
order  to  employ  them  correctly  the  key  is  needed,  and 


40  SINGLE-LIQUID  BATTERIES. 

this  may  be  found  in  the  old  theoretical  ideas  upon  the 
two  electric  fluids,  the  one  positive  and  the  other  nega- 
tive. There  is,  at  each  point  in  a  circuit  through  which 
a  current  flows,  a  reuniting  of  positive  and  negative  elec- 
tricity ;  the  negative  electricity  of  the  oxygen  is  attracted 
by  the  positive  electricity  of  the  positive  electrode,  and 
so  on.  This  circuit  is  considered  as  a  chain,  in  which 
one  end  of  each  link  is  positive  and  the  other  nega- 
tive. 

The  theoretical  ideas  have  changed,  but  the  expressions 
have  remained,  the  alteration  of  which  would  only  involve 
difficulties,  because  they  are  not  in  disagreement  with  the 
new  scientific  views.  We  will  not  enter  into  the  details 
of  this  demonstration,  but  will  return  to  the  exact  appli- 
cation of  these  terms,  in  order  to  spare  the  reader  the 
annoyance  of  certain  errors  to  which  he  may  be  exposed. 

In  general,  every  liquid  decomposed  by  the  passage  of 
an  electric  current  is  called  an  electrolyte,  and  it  is  said  to 
be  electrolysed  as  long  as  the  electric  action  continues. 
Faraday  has  established,  by  numerous  experiments,  the 
laws  of  definite  electrolysis.  We  cannot  enlarge  upon 
this  delicate  subject.  We  will  only  say  that,  if  two  or 
three  cells  joined  in  intensity  produce  a  current  used  to 
electrolyze  water,  for  instance,  for  each  chemical  equiv- 
alent of  hydrogen  set  free  in  the  voltameter  there  will 
be  an  equivalent  of  zinc  dissolved  in  each  cell  of  the 
battery.  The  law  of  Faraday  may  be  said  to  be  the 
equivalence  of  chemical  work  in  all  parts  of  the  cir- 
cuit. 

If  the  experiment  be  made  with  six  cells,  instead  of 
with  three  as  indicated  above,  the  quantity  of  hydrogen 
set  free  in  one  minute  is  much  greater.  An  idea  of  the 
quantity  of  electricity  is  thus  obtained,  and  it  can  be  un- 


GENERAL   EEMARKS    UPON   BATTERIES.  41 

derstood  how  the  instrument  called  voltameter  permits 
one  to  measure  this  quantity.  It  owes  its  name  to  Fara- 
day, who  was  perfectly  justified  in  so  calling  it,  as  it  is 
in  truth  an  instrument  of  measurement.  The  same  can- 
not be  said  of  the  galvanometer,  which  it  would  be  better 
to  call  galvanoscope  ;  for  in  general  it  does  not  measure 
the  intensity  of  the  current  which  passes  through  it,  and 
it  is  only  by  means  of  complicated  contrivances  that  any 
measurements  can  be  obtained  from  its  indications. 

Unhappily  the  voltameter  is  not  convenient  for  use.  In 
many  cases  it  gives  no  indications,  and  in  others  produces 
false  results,  on  account  of  the  resistance  which  it  intro- 
duces into  the  circuit.  It  presents  other  causes  of  error, 
as  will  be  seen  in  the  following  pages. 

SECONDARY  CURRENTS. 

POLARIZED    ELECTRODES. 

If  the  voltameter  be  submitted  for  a  short  time  to  the 
action  of  a  current,  its  electrodes  acquire  remarkable 
properties,  which  may  be  recognized  in  the  following 
manner : 

Detach  the  wires  connecting  the  voltameter  to  the  bat- 
tery, and  then  connect  the  voltameter  with  a  galvanome- 
ter ;  the  galvanometric  needle  will  be  seen  to  deflect,  thus 
making  manifest  the  passage  of  a  current  furnished  by 
the  voltameter.  The  direction  of  the  current  is  such  as 
to  show  that  that  which  was  the  negative  electrode  of  the 
voltameter  in  the  experiment  with  the  battery  has  be- 
come, in  the  experiment  with  the  galvanometer,  the  posi- 
tive pole  of  this  new  source  of  electricity.  In  other 
words,  the  current  flows  in  one  direction  in  the  first  case, 
and  in  the  opposite  direction  in  the  second  case.  It  may 


42  SINGLE-LIQUID  BATTERIES. 

be  said  that  the  voltameter  has  been  charged  with  a  part 
of  the  current  of  the  battery,  and  that  the  voltameter  re- 
turns this  current  in  the  contrary  direction. 

It  has  been  said  that  the  electrodes  are  polarized,  which 
is  indeed  true ;  for  they  have  been  rendered  capable  of 
acting  as  poles.  This  is  the  origin  of  the  expression 
polarization  of  the  electrodes  which  we  have  already  used, 
and  which  we  will  frequently  have  occasion  to  employ. 

The  current  furnished  by  the  polarized  electrodes  of 
the  voltameter  in  the  conditions  indicated  above  is  called 
a  secondary  current ;  the  voltameter  acts  as  a  secondary 
battery.  The  secondary  current  thus  obtained  lasts  but  a 
short  time,  and  its  intensity  is  seen  to  diminish  rapidly 
from  the  moment  it  begins  to  circulate  in  the  galvanome- 
ter and  is  soon  reduced  to  nothing. 

"We  will  again  have  occasion  to  speak  of  secondary  bat- 
teries, of  which  we  have  just  given  an  example,  and  which 
have  lately  undergone  vast  improvements. 

POLARIZATION  OF  A  VOLTAIC  CELL. 

If  the  current  furnished  by  a  voltaic  cell  (one  of  Wol- 
laston's,  for  instance)  with  well-amalgamated  zinc  be 
examined  by  means  of  a  galvanometer,  the  intensity  is 
seen  to  diminish  from  the  moment  the  circuit  is 
closed. 

This  diminution  is  very  rapid  if  the  circuit  has  but 
very  little  resistance  ;  it  is,  on  the  other  hand,  very  slow 
if  the  circuit  offers  great  resistance,  as  in  a  long  line  of 
telegraph. 

If,  after  having  allowed  the  current  to  flow  for  five 
minutes,  for  instance,  the  circuit  be  left  open  for  five 
minutes,  it  will  be  seen  when  again  closed  that  the  cur- 


GENERAL   REMARKS    UPON   BATTERIES.  43 

rent  has  nearly  assumed  its  first  intensity.  It  can  be  said 
then,  the  battery  when  not  at  work  regains  its  initial 
power. 

It  may  be  understood  from  these  observations  how  it 
has  been  possible  to  use  the  sand-battery  for  a  number  of 
years  in  the  telegraph  service  ;  the  telegraph  lines  offer- 
ing indeed  great  resistances,  but  only  needing  intermit- 
tent currents. 

By  closely  examining  that  which  takes  place  while  the 
circuit  is  closed,  different  circumstances  of  the  phenome- 
non will  be  seen,  which  will  throw  a  great  deal  of  light 
upon  the  causes  to  which  it  must  be  attributed. 

At  first  bubbles  of  hydrogen  are  seen  to  form  them- 
selves upon  the  copper  electrode,  as  we  have  already 
stated  ;  this  will  lead  to  the  belief  that  imperceptible 
bubbles  form  themselves  upon  the  entire  surface  in  such 
a  way  as  to  interpose,  more  or  less  completely,  between 
the  electrode  and  the  liquid,  a  gaseous  layer.  Thus  appar- 
ently the  principal  cause  of  the  diminution  in  the  intensity 
of  the  current  should  be  sought  at  the  surface  of  the  cop- 
per electrode. 

Several  simple  experiments  will  confirm  this. 

If,  after  a  marked  diminution  in  the  deflection  of  the 
galvanometric  needle,  the  electrodes  be  shaken  without 
lifting  them  out  of  the  liquid,  the  current  is  seen  to  partly 
recover  the  force  it  had  lost. 

The  same  thing  is  observed  if  the  liquid  alone  be 
shaken  without  moving  the  electrodes,  and  consequently 
without  changing  the  extent  of  the  immersed  surface. 

The  moving  of  the  copper  electrode  alone  will  show, 
as  a  result,  the  recovery  of  the  lost  force. 

By  rubbing  the  copper,  without  taking  it  out  of  the 
liquid,  with  a  small  brush,  the  same  result  is  noticed. 


44  SINGLE-LIQUID  B-ATTEKIES. 

In  these  three  experiments  the  disappearance  of  bubbles 
of  hydrogen  from  the  surface  of  the  conducting  electrode 
is  accompanied  by  a  renewal  of  the  intensity  of  the  current. 

If,  on  the  other  hand,  the  zinc  electrode  alone  be  agi- 
tated, no  perceptible  modification  in  the  decrease  of  the 
current  takes  place. 

Henceforth  there  can  be  no  doubts  as  to  the  impor- 
tance of  the  phenomenon  which  takes  place  at  the  surface 
of  the  copper  electrode.  The  diminution  of  intensity 
that  we  have  observed  may  be  attributed  to  two  causes : 
either  to  the  increase  in  the  internal  resistance  of  the 
battery,  or  to  the  decrease  in  the  electro-motive  force. 
In  fact,  the  two  causes  are  present  at  the  same  time. 
That  the  resistance  increases  cannot  be  doubted,  since  the 
active  surface  of  the  copper  electrode  is  diminished  ;  but 
a  simple  and  direct  demonstration  of  this  does  not  seem 
easy  to  obtain. 

That  the  electro-motive  force  is  diminished  is  ex- 
tremely easy  to  demonstrate.  For  this  experiment  we 
employ  the  method  of  opposition  which  we  have  already 
described,  and  which  is  as  convenient  for  the  comparison 
of  electro-motive  forces  as  are  scales  for  the  comparison 
of  weights. 

The  instant  the  electrodes  are  immersed  in  the  liquid 
and  the  battery  begins  to  work,  it  attains  its  maximum 
intensity. 

Let  us  now  take  two  identical  battery  cells  and  close 
the  circuit  of  one  of  them  for  five  minutes,  leaving  the 
other  inactive.  At  the  expiration  of  five  minutes,  place 
the  one  that  has  been  working  in  opposition  to  the  fresh 
one,  and  a  galvanometer  interposed  in  the  circuit  will 
show  the  superiority  of  the  electro-motive  force  of  the 
fresh  cell. 


GENERAL   KEMARKS   UPON   BATTERIES.  45 

If  now  these  two  cells  be  made  to  act  separately,  each 
upon  itself — that  is,  without  the  insertion  of  any  resist- 
ance during  five  minutes — it  will  be  found  at  the  end  of 
that  time,  by  placing  them  in  opposition,  that  the  second 
one  still  has  a  greater  electro-motive  force  than  the  first 
one. 

The  experiments  could  be  varied,  and  it  could  be  ascer- 
tained, for  instance,  how  long  the  decrease  continues  in  a 
cell  of  a  certain  size  and  form  and  under  well-known 
circumstances. 

It  can  be  easily  shown  that  the  electro-motive  force  of 
a  voltaic  cell  can,  by  constant  action,  be  reduced  one 
half.  For  this  it  is  only  necessary  to  cause  two  cells  to 
work  a  considerable  length  of  time ;  when  they  are  sup- 
posed to  be  exhausted  as  much  as  they  can  be,  join  them 
in  intensity  and  place  this  battery  of  two  cells  in  opposi- 
tion to  an  entirely  new  cell ;  the  galvanometer  will  still 
mark  the  superiority  of  the  latter,  and  the  necessary  con- 
clusion is  that  the  electro-motive  force  of  each  one  of  the 
two  exhausted  cells  has  been  reduced  to  less  than  half  of 
that  of  the  new  cell. 

It  is  admitted  that  the  diminution  in  the  electro-motive 
force  of  batteries  is  due  to  the  production  of  an  electro- 
motive force  (upon  the  surface  of  the  negative  electrode) 
contrary  to  that  of  the  principal  current. 

This  view  is  founded  upon  that  which  we  have  said  of 
the  electro-motive  force  found  in  a  voltameter,  from 
whose  electrodes  gases  are  given  off. 

It  may  be  shown  by  a  direct  experiment  that  the  con- 
ducting electrode  C  of  a  weakened  battery  has  acquired 
peculiar  properties.  It  is  only  necessary  to  immerse  in 
the  liquid  a  second  plate  of  copper,  C',  and  to  connect  the 
two  with  a  galvanometer.  The  passage  of  a  current  is 


46  SINGLE-LIQUID  BATTERIES. 

thus  made  manifest,  and  its  direction  shows  that  the 
copper  plate  C  acts  as  the  soluble  electrode,  or  electro- 
positive, when  compared  with  the  other,  C',  which  assumes 
the  part  of  a  conducting  electrode,  or  electro-negative. 
This  current  commences  to  decrease  from  the  moment  it 
is  established,  and  soon  becomes  imperceptible.  Thus  the 
electrode  C,  which  was  electro-negative  in  the  voltaic  cell 
before  and  during  its  weakening,  is  electro-positive  in  the 
test  cell  of  two  copper  electrodes.  Finally,  if  after  the 
above  experiment  the  voltaic  cell  be  re-established,  it  as- 
sumes its  original  intensity,  at  least  for  a  moment,  and 
then  .begins  to  weaken  again,  as  in  the  first  instance. 

It  is  then  that  the  conducting  electrode  is  said  to  be  in 
a  state  of  polarization. 

Such  is  the  phenomenon  of  the  polarization  of  the 
negative  electrode  of  batteries,  a  knowledge  of  which  is 
so  important. 

It  will  be  seen,  in  the  following  pages  of  this  work, 
that  the  less  the  polarization,  the  better  the  batteries. 
The  most  important  improvements  in  batteries  are  those 
which  have  had  in  view  the  diminution  or  suppression  of 
polarization.  In  other  words,  the  principal  aim  and  effort 
of  inventors  worthy  of  that  name  has  been  to  depolarise 
the  electrode. 

It  has  been  established  that  polarization  remains  the 
same  when  the  size  of  the  cell  and  the  intensity  of  the 
current  are  in  proportion  to  each  other.  It  is  here  neces- 
sary to  define  polarization :  it  is  the  difference  between 
the  electro-motive  forces  in  a  polarized  battery  and  a 
depolarized  battery. 

It  can  be  understood  indeed  that  the  quantity  of 
hydrogen  given  off  upon  the  negative  electrode  is  in 
proportion  to  the  intensity  of  the  current  5  and  that  if 


GENERAL   REMARKS   UPON   BATTERIES.  47 

this  quantity  distributes  itself  upon  the  surface  of  an 
electrode  also  proportional,  the  thickness  of  the  deposit 
will  be  the  same,  and  consequently  its  intrinsic  action 
will  not  have  changed.  The  practical  conclusion  of  this 
law  is  that  polarization  will  be  less  in  a  battery  having 
large  electrodes  than  in  a  smaller  one,  although  the  total 
resistance  be  the  same. 

POLARIZATION  IN  A  BATTERY  OF  SEVERAL 
ELEMENTS. 

Thus  far,  each  time  that  we  have  spoken  of  the  polari- 
zation of  the  negative  or  conducting  electrode  of  cells, 
we  have  implicitly  supposed  the  cell  to  be  alone,  and 
that  the  current  which  produced  the  polarization  was  the 
current  of  the  cell  itself.  In  ordinary  practice  it  is  not 
thus ;  several  elements  are  generally  joined  in  intensity, 
and  the  current  which  flows  in  each  one  is  furnished  by 
the  entire  battery. 

Let  us  place  10  cells,  each  having  10  units  of  resistance, 
in  a  circuit  of  100  units  (total  resistance  200  units) ;  it  is 
clear  that  the  current  will  be  more  intense  than  if  9  of 
the  10  cells  were  taken  away ;  consequently  the  current 
which  produces  the  polarization  in  each  cell  will  be  more 
energetic  than  if  there  were  only  one  cell. 

The  result  is  that  the  weakening  due  to  polarization  is 
more  marked  in  cells  which  are  joined  in  intensity  than 
when  they  are  separate. 

In  other  words,  when  a  current,  passing  through  a  cell, 
'is  more  energetic  than  the  current  which  the  cell  itself 
produces,  the  weakening  of  the  current  takes  place  under 
the  following  circumstances  : 

At  first  hydrogen  is  given  off  upon  the  copper,  and 


48  SINGLE-LIQUID  BATTERIES. 

produces  that  which  we  have  termed  polarization  of  the 
cell. 

But  afterwards,  when  the  greater  part  of  the  acid  is 
converted  into  sulphate  of  zinc,  the  sulphate  itself  be- 
comes electrolyzed  and  reduced  zinc  deposits  itself  upon 
the  copper.  If  at  last  this  deposit  covers  the  entire  sur- 
face of  the  copper,  it  can  be  easily  seen  that  the  two 
electrodes  will  become  identical,  and  consequently  it  is 
no  longer  a  battery  cell. 

We  shall  show  instances  where  some  of  the  cells  of  a 
battery  not  only  cease  to  produce  a  current  in  the  right 
direction,  but  actually  produce  a  reverse  current. 


CHAPTER   IV. 
SULPHURIC-ACID  BATTERIES. 

AT  the  point  which  we  have  now  reached  we  are  able 
to  compare  different  batteries  and  to  undertake  their 
study. 

Up  to  this  time  we  have  only  shown  Yolta's  battery 
and  the  modifications  in  its  arrangement.  We  will  now 
examine  batteries  which  are  analogous,  but  which  differ 
more  and  more  from  the  first  model. 

This  study  will  show  how  Yolta,  in  spite  of  his  imper- 
fect means,  happily  chose  the  elements  which  have  been 
used  ever  since ;  it  will  be  seen  how  advantageous  and 
how  imperative  the  use  of. zinc  is. 

We  will  first  study  those  batteries  in  which  the  liquid 
is  dilute  sulphuric  acid,  but  in  which  the  electrodes  differ 
from  those  in  the  voltaic  battery. 

BATTEEIES  WITH  CARBON  ELECTRODES. 

A  battery  differing  from  Yolta's  only  in  the  substitu- 
tion of  carbon  electrodes  for  those  of  copper  is  very 
often  employed ;  it  was  invented  by  Mr.  Walker  in  1849. 

In  these  cells  the  negative  electrodes  are  made  of  gas 
carbon,  which  forms  a  shell  upon  the  heated  retorts  in 
the  preparation  of  gas.  This  substance  has  a  very  good 
conducting  power,  and  it  is  very  porous.  On  account  of 
this  porosity  the  electrode  presents  a  considerable  surface, 
and  is  very  slowly  polarized. 


50  SINGLE-LIQUID  BATTERIES. 

We  have  already  explained,  in  speaking  of  Wollaston's 
battery,  why  it  was  advantageous  to  give  the  largest  sur- 
face possible  to  the  conducting  electrode  from  which 
hydrogen  is  given  off.  The  method  that  we  have  given 
to  show  the  progress  of  polarization  in  a  battery  cell  proves 
the  superiority  of  a  battery  with  carbon  electrodes  over 
that  of  Volta  of  equal  dimensions. 

The  zinc  may  be  placed  between  two  plates  of  carbon, 
or  better  still  in  the  centre  of  a  hollow  cylinder  of  car- 
bon, always  having  in  view  the  increase  of  the  surface  to 
be  polarized  and  the  checking  of  the  polarization. 

MANUFACTURE  OF  CARBON  ELECTRODES. 

When  carbon  electrodes  have  simple  geometrical  forms, 
or  when  they  are  simple  plates  more  or  less  thick  and 
wide,  they  may  easily  be  cut  from  the  residue  in  gas- 
retorts,  and  that  is  what  is  generally  done. 

But  if  they  are  cylindrical,  and  especially  hollow  cylin- 
ders like  that  shown"  in  Fig.  18,  the  above  process  cannot 
be  applied.  The  electrodes  must  be  produced  artificially 
in  moulds,  by  pressing  powdered  carbon  with  proper 
cements. 

Bunsen  suggests  the  following  process  to  make  carbon  : 

A  mixture  of  one  part  by  weight  of  coal  and  two  of 
coke  is  made  (both  having  been  reduced  to  an  impalpable 
powder),  which,  placed  in  a  sheet-iron  mould,  is  heated  to 
clear  red  until  all  gases  have  been  given  off.  The  carbon 
is  then  dipped  in  molasses  and  left  to  calcinate,  protected 
from  the  air. 

John  T.  Sprague,  of  Birmingham,  recommends  the 
following  process : 

"Plates  or  blocks  may  be  built  up  from  powdered 


SULPHURIC-ACID  BATTERIES.  51 

graphite  mixed  up  with  coal-tar  or  strong  rice-paste 
into  a  stiff  dough,  which  should  be  dried,  heated,  then 
packed  in  powdered  carbon  in  a  closed  vessel  and  heated 
to  clear  red  for  some  time.  When  cool  they  should  be 
soaked  in  strong  syrup  of  sugar,  or  treacle,  again  dried 
and  treated  as  before ;  this  process  must  be  repeated 
until  the  carbon  is  perfectly  dense  and  strong." 


FIG.  18. 

USE  OF  CAEBOX  ELECTKODES. 

The  chief  difficulty  with  carbon  is  in  making  the  con- 
nection. The  contact  between  the  carbon  and  the  me- 
tallic rheophore,  by  which  it  is  connected  with  the  adjoin- 
ing cell  or  with  the  circuit,  must  be  perfect. 

This  is  commonly  done  by  fixing  a  clamp  on  it  to  which 
the  rheophores  are  attached. 


52  SINGLE-LIQUID  BATTERIES. 

A  better  plan  is  to  deposit  copper  on  the  upper  part 
and  then  solder  the  connection  to  it,  as  this  gives  continu- 
ous circuit.  There  is  one  drawback,  however :  the  acid 
is  soaked  by  capillary  action  into  the  pores  of  the  sub- 
stance, reaches  the  surface  of  the  carbon  and  the  inner 
surface  of  the  copper,  which  it  attacks,  thus  destroying 
the  connection.  It  is  easy  to  avoid  this  action  by  im- 
mersing the  upper  part  of  the  carbon  in  melted  paraffin. 
The  pores  of  the  immersed  part  are  thus  filled  by  the 
paraffin,-  which,  when  left  to  cool,  becomes  solid.  All 
capillary  action  through  the  upper  part  of  the  carbon  is 
thus  prevented. 

The  top  of  the  carbon  may  also  be  immersed  in  melted 
zinc.  But  by  capillarity  the  liquid  can  ascend  and  attack 
the  zinc  as  it  did  the  copper.  The  sulphate  of  zinc 
would  present  the  same  difficulties  as  the  sulphate  of  cop- 
per, and  it  is  also  desirable  in  this  case  to  dip  the  upper 
part  of  the  carbon  in  paraffin.  The  experiment  shows 
that  paraffin  does  not  affect  the  conductivity  of  the  car- 
bon, and  that  the  resistance  of  the  battery  is  not  increased 
by  this  addition. 

Lead  may  also  be  deposited  upon  the  top  of  the  carbon, 
but  here  the  paraffin  is  indispensable,  because  the  forma- 
tion of  sulphate  of  lead  is  enough  to  diminish  consider- 
ably the  intensity  by  introducing  in  the  current  a  matter 
almost  without  conductivity  and  nearly  insoluble. 

In  Switzerland  the  battery  which  we  have  above  de- 
scribed is  extensively  used,  especially  in  telegraph  offices. 
The  zinc  should  be  well  amalgamated  before  being  placed 
in  the  centre  of  the  carbon  cylinder  (Fig.  18),  in  order 
to  diminish  local  actions  while  the  battery  is  at  rest; 
owing  to  this  precaution  the  battery  may  be  used  a  long 
time  without  any  care  being  bestowed  upon  it. 


SULPHURIC-ACID   BATTERIES.  53 

We  will  see  farther  on  how  this  battery  has  been  inv 
proved  upon  by  substituting  a  solution  of  sea-salt  for  the 
dilute  sulphuric  acid. 

ZINC-IKON  BATTEKY. 

One  of  the  first  ideas,  and  the  most  natural,  is  to  use 
iron  on  account  of  its  cheapness.  Iron  may  indeed  be 
substituted  for  the  copper,  but  a  battery  thus  arranged  is 
very  inferior  to  that  of  Yolta.  The  substitution  of  iron 
for  copper  causes  a  notable  diminution  in  the  electro- 
motive force.  It  is  important  to  note,  however,  that  the 
copper  may  be  effectively  replaced  by  iron  ;  that  it  is  still 
the  zinc  which  is  attacked ;  and  that  the  iron  is  preserved 
from  the  action  of  the  sulphuric  acid  while  the  circuit  is 
closed. 

IKON-COPPER  BATTEKY. 

In  Yolta's  battery  it  is  the  zinc  which  is  continuously 
dissolved  ;  it  is  therefore  logical  to  search  for  something 
which  may  replace  the  zinc  and  which  at  the  same  time 
is  less  costly — iron,  for  instance.  This  substitution  of 
iron  for  zinc  would  be  more  advantageous  than  the  sub- 
stitution of  iron  for  copper ;  but  this  battery  (iron,  cop- 
per, and  sulphuric  acid)  is  still  inferior  to  the  preceding 
one. 

OTHEK  COMBINATIONS. 

If  the  question  of  economy  be  put  aside,  many  other 
combinations  might  be  usefully  employed ;  but,  as  we 
have  said,  the  use  of  zinc  is  necessary,  as  no  other  metal 
practically  acceptable  can  be  advantageously  substituted. 


54  SINGLE-LIQUID  BATTERIES. 

Even  aluminium  is  less  liable  to  be  attacked,  or,  as  it  is 
said,  is  less  electro-positive  than  the  zinc.  Only  calcium, 
sodium,  potassium,  and  analogous  metals  are  more  electro- 
positive. It  is  needless  to  say,  however,  that  they  cannot 
be  used  in  batteries  destined  for  practical  purposes. 

For  the  negative  or  insoluble  electrode  there  is,  on  the 
other  hand,  great  choice :  lead,  silver,  and  platinum  can 
be  and  are  often  employed.  The  electro-motive  force  of 
a  zinc-platinum  battery  is  rather  superior  to  that  of  Yol- 
ta's  (zinc-copper),  and  is  about  equal  to  the  zinc-carbon 
battery. 

Following  is  a  list  of  metals  so  arranged  that  if  any 
two  be  taken  to  form  the  electrodes  of  a  dilute  sulphuric- 
acid  battery,  the  one  nearest  the  end  of  the  list  will  be 
the  positive  electrode,  or  the  negative  pole  of  the  cell  thus 
arranged  : 


1.  Silver. 
2.  Copper. 
3.  Antimony. 

4.  Bismuth. 
5.  Nickel. 
6.  Iron. 
7.  Lead. 

8.  Tin. 
9.  Cadmium. 
10.  Zinc. 

Too  great  an  importance  must  not  be  attached  to  this 
list,  for  the  order  of  the  metala  would  be  different  if  the 
liquid  were  other  than  dilute  sulphuric  acid. 

SMEE'S  CELL. 

Many  ways  have  been  devised  for  reducing  the  polari- 
zation of  the  negative  electrode  of  the  batteries  which 
we  have  described.  In  1840  Smee  indicated  a  very  inge- 
nious way,  which  consists  in  using  electrodes  of  platinum, 
upon  whose  surface  he  deposited,  by  means  of  electricity, 
platinum  as  a  fine  black  powder.  These  electrodes  of 


SULPHURIC-ACID   BATTERIES.  55 

platinized  platinum  tend  to  diminish  considerably  po- 
larization. The  simple  reason  of  this  is  that  the  bubbles 
of  hydrogen  free  themselves  much  more  easily  than  from 
the  polished  surface  of  a  metal. 

For  reasons  of  economy  Smee  placed  the  platinum 
plate  between  the  two  plates  of  zinc.  It  is  in  form  a 
reversed  Wollaston  battery. 

Smee's  battery  is  charged  with  a  solution  containing 
one  part  of  acid  to  seven  parts  of  water.  Its  work  is 
much  greater  than  could  be  expected  from  a  single-liquid 
battery. 

Again,  for  economy,  Smee  replaced  the  platinized 
platinum  by  platinized  silver.  The  following  composition 


FIG.  19. 

had  even  been  used,  which  produces  a  much  cheaper 
cell: 

Upon  a  plate  of  copper  is  deposited  a  grainy  layer  of 
copper,  then  a  layer  of  silver,  and  finally  a  layer  of  plati- 
num dust.  The  rough  surface  thus  given  to  the  silver 
facilitates  the  deposit  of  platinum,  which  is  very  difficult 
upon  polished  silver. 


56  SINGLE-LIQUID  BATTERIES. 

One  of  Smee's  batteries  would  give  very  unsatisfactory 
results  if  the  zinc  were  not  amalgamated ;  it  is  a  precau- 
tion that  should  not  be  neglected. 

This  battery  is  extensively  used  in  England  and  the 
United  States  with  many  modifications,  one  of  which  is 
presented  by  Fig.  19. 

WALKER'S  PLATINIZED  CARBON  BATTERY. 

We  have  stated  above  how,  since  1849,  Walker  had 
used  batteries  with  electrodes  of  carbon  cut  from  the 
gas-retorts.  In  1857  he  resolved  to  platinize  his  carbons, 
and  the  battery  thus  constructed  has  been  used  by  the 
South-Eastern  Railway  in  England  with  great  success  ; 
nine  thousand  of  these  cells  were  in  service  in  March, 
1875. 

These  cells  are  contained  in  an  earthen  jar,  and  the 
lower  extremity  of  the  zinc  is  immersed  in  a  gutta-percha 
saucer  filled  with  mercury ;  the  zinc  is  wrell  amalgamated, 
which  reduces  to  its  minimum  the  local  action  or  lo£i 
chemical  work;  the  top  part  of  the  carbon  is  copper- 
plated  and  tinned. 

The  usual  size  of  these  cells  is  4  inches  by  2  inches ; 
their  price  (with  the  mercury  and  sulphuric  acid),  42  cents. 

The  cost  of  keeping  them  in  order  is  calculated  at  25 
cents  annually. 

This  battery  may  be  left  twelve,  fifteen,  and  sometimes 
seventeen  months  without  needing  any  care  whatever. 

It  is  a  simple  modification  of  Smee's  battery,  and  with 
a  liquid  of  one  part  of  acid  to  eight  parts  of  water  there 
is  an  electro-motive  force  equal  to  that  of  Smee's  (meas- 
urements made  before  any  polarization).  Polarization 
may  reduce  the  electro-motive  force  one  half.  It  will 


SULPHUEIC-ACID   BATTERIES. 


57 


be  seen  from  the  tables  at  the  end  of  this  work  that  this 
force  is  equal  to  that  which  is  taken  as  the  unit ;  namely, 
that  of  Darnell's  battery. 

The  internal  resistance  of  Walker's  battery  is  about 
1  ohm,  or  1  unit.  It  is  certainly  a  very  small  resistance 
for  a  telegraph  battery,  a  quality  which  we  must  point 
out. 

TYEE'S  BATTERY. 

Tyer  combined  a  modification  of  Smee's  batteries,  for 
the  service  of  electric  railroad  signals,  which  presents 
many  advantages. 


FIG.  20. 


In  the  bottom  of  the  jar  (Fig.  20)  are  placed  a  sufficient 
quantity  of  mercury  and  pieces  of  zinc  ;  this  constitutes 
the  generating  electrode. 

A  plate  of  platinized  silver  is  held  vertically  in  the  jar 


58  SINGLE-LIQUID  BATTERIES. 

by  means  of  a  cross-piece  of  lead  which  rests  on  the  rim 
of  the  jar,  thus  giving  a  good  height  and  a  certain  firm 
ness  to  the  conducting  electrode.  The  top  of  the  cross- 
piece  of  lead  is  furnished  with  a  terminal,  to  which  is 
fastened  a  copper  wire  covered  with  gutta-percha ;  at 
the  end  of  this  wire  is  a  ball  of  zinc  which  is  wholly 
immersed  in  the  mercury  of  the  adjoining  cell. 

The  liquid  is  sulphuric  acid  diluted  with  twenty  times 
its  volume  of  water. 

This  battery  has  the  advantage  of  consiiming  frag- 
ments of  zinc  and  using  them  to  their  last  particle.  Those 
pieces  which  are  wasted  in  the  manufacture  of  other  bat- 
teries can  here  be  put  to  use.  In  this  respect  Tyer's  is 
the  best  arrangement  yet  produced. 

The  maintenance  of  this  battery  is  reduced  to  a 
minimum,  for  in  a  well-closed  box  it  can  remain  two  or 
three  years  without  examination.  Great  care  should  be 
taken,  however,  in  the  charging  and  cleaning  of  the  bat- 
tery, in  order  to  avoid  any  loss  of  mercury. 

BARON  EBNER'S  BATTERY. 

To  the  Austrian  general,  Baron  Ebner,  is  due  the  fol- 
lowing arrangement  of  Smee's  battery.  The  negative 
electrode  is  of  platinized  lead ;  the  generating  electrode 
is,  as  in  the  preceding  arrangement,  composed  of  frag- 
ments of  zinc  in  some  mercury,  which  keeps  them  well 
amalgamated. 

A  very  large  battery  of  this  kind  was  used  at  the 
Paris  Exposition  of  1867  to  run  electric  clocks ;  which 
proved  that  the  polarization  was  but  slightly  felt,  as 
electric  clocks  do  not  work  well  unless  a  very  constant 
current  is  provided. 

The  electro-motive  force  of  this  battery  is  only  about 


SULPHURIC-ACID   BATTEEIES.  59 

•half  that  of  Daniell's  battery,  of  which  we  will  speak 
farther  on,  and  which  is  generally  taken  as  a  term  of 
comparison.  Its  maintenance  is  very  economical,  for  the 
same  reasons  given  in  the  description  of  Tyer's  battery. 

BATTEKIES  ANALOGOUS  TO  THAT  OF  SMEE. 

Following  Smee's  example,  Poggendorff  deposited  pul- 
verized copper  upon  a  copper  electrode  and  thus  obtained 
a  battery  of  Volta,  or  of  Wollaston,  notably  improved, 
inasmuch  as  the  polarization  takes  place  less  rapidly  and 
with  less  intensity. 

Drivet,  an  Italian  officer,  carried  out  an  analogous  idea. 
He  deposited  upon  the  copper  electrode  of  a  voltaic  cell 
a  very  thick  layer  (£  of  an  inch)  of  spongy  copper.  The 
porosity  of  this  metal  gives  it  some  of  the  qualities  of 
carbon  electrodes.  The  analogy  with  Smee's  battery  is 
more  apparent  than  real,  for  the  very  thin  layer  of  pul- 
verized platinum  does  not  present  the  increase  of  surface 
which  is  the  advantage  in  the  use  of  carbon  electrodes. 

We  have  ourselves  tried  a  battery  in  which  the  nega- 
tive electrode  is  a  plate  of  lead,  upon  whose  surface  a 
layer  of  spongy  lead  -fa  of  an  inch  thick  is  deposited. 

REMARKS  UPON  POLARIZATION  IN  THE 
PRECEDING  BATTERIES. 

"We  have  seen  in  all  batteries  described  thus  far  that 
polarization  was  the  result  of  the  freeing  of  gaseous  bub- 
bles of  hydrogen  from  the  negative  electrode. 

We  have  indicated  several  means,  devised  by  different 
physicists,  to  diminish  this  effect,  which  is  done  either 
by  increasing  the  surface  of  the  electrode  to  be  polarized 
(Wollaston's  battery,  carbon-electrode  battery,  and  Dri- 


60  SINGLE-LIQUID  BATTERIES. 

vet's  battery)  or  by  modifying  this  surface  in  such  a  way 
as  to  facilitate  the  freeing  of  the  gas  (Smee's  and  similar 
batteries).  The  action  of  a  battery  is  already  vastly  im- 
proved by  giving  a  rough  surface  to  the  polarized  elec- 
trode, instead  of  leaving  it  polished. 

We  have  also  shown  how  the  air  acts  favorably  upon 
batteries,  either  by  diminishing  polarization  while  they 
are  at  work  or  by  producing  depolarization  when  the 
current  has  ceased  to  flow.  Depolarization  would  un- 
doubtedly take  place  in  the  absence  of  the  oxygen  of  the 
air,  by  the  freeing  of  gas  or  by  its  dissolution  in  the 
liquid ;  but  the  oxyen  renders  depolarization  much  more 
rapid,  especially  in  the  case  of  carbon  electrodes,  by  com- 
bining with  the  hydrogen  to  form  water. 

"We  will  indicate,  as  we  proceed,  much  more  effectual 
means  for  diminishing  or  suppressing  polarization,  which 
consist  in  the  use  of  substances  placed  near  the  negative 
or  conducting  electrode,  and  by  which  the  hydrogen  is 
chemically  absorbed.  These  are  the  only  contrivances 
by  which  constant  batteries  can  be  produced  ;  that  is, 
batteries  whose  electro-motive  force  is  constant. 

We  will  describe  in  detail  these  constant  batteries, 
which  present  a  satisfactory  solution  of  the  problem  of 
obtaining  a  continuous  and  regular  electric  current. 
They  have  taken  the  place  of  simple  and  inconstant 
batteries  in  all  applications,  and  their  study  will  be  the 
crowning  of  the  present  work. 

But  in  order  to  proceed  from  the  simple  to  the  com- 
plex we  ought  to  describe  seve-ral  other  inconstant  bat- 
teries, only  a  few  of  which  have  any  practical  interest. 
Their  study  is,  however,  necessary  in  order  to  under- 
stand the  many  varieties  already  tried  and  those  which 
might  be  tried. 


CHAPTEE  V. 
ACID  BATTERIES  ANALOGOUS  TO  THAT  OF  VOLTA. 

THUS  far  we  have  considered  a  series  of  batteries  dif- 
fering very  little  from  each  other,  all  being  composed  of 
two  different  electrodes  immersed  in  a  single  liquid,  di- 
lute sulphuric  acid. 

It  is  easily  understood  that  by  replacing  the  sulphuric 
acid  by  other  acids,  new  batteries  analogous  to  the  first 
ones  may  be  obtained. 

HYDEOCHLOEIC-ACID  BATTEEIES. 

The  cheapness  of  hydrochloric  acid  caused  many  per- 
sons to  use  it ;  but  none  of  the  batteries  thus  constructed 
obtained  any  continued  application,  because  hydrochloric 
acid,  being  gaseous  and  only  soluble  in  water,  escapes  into 
the  surrounding  air,  so  that  after  a  short  time  it  is  im- 
possible to  remain  in  the  room  where  it  is  placed. 

Besides,  the  hydrochloric  acid  liberates  itself  rapidly 
from  the  water  in  which  it  is  dissolved,  at  least  a  good 
part  of  it,  the  liquid  becoming  immediately  impoverish- 
ed;  and  a  new  cause  of  the  weakening  of  the  current  is 
added  to  those  which  we  have  already  pointed  out. 

OTTKIC-ACID  BATTEEIES. 

Nitric-acid  batteries  could  be  very  easily  made,  but 
they  would  have  the  same  inconveniences  as  those  with 


62  SINGLE-LIQUID  BATTEEIES. 

hydrochloric  acid,  and  would  not  present  the  same  eco- 
nomical advantage.  It  will  be  seen,  however,  that  in  cer- 
tain less  rudimentary  combinations  nitric  acid  is  put  into 
use. 

YAEIOUS  ACID  BATTERIES. 

All  acids  employed  by  chemists  maybe  used  in  the 
composition  of  batteries,  provided  they  be  liquid  or  solu- 
ble in  water  and  conductors  of  electricity. 

Acetic  acid,  found  in  all  households,  may  be  used  in 
the  absence  of  others.  It  has  indeed  been  used  by  Pul- 
vermacher  in  his  electro-medical  battery.  The  electrodes 
were  zinc  and  copper  wires  wound  upon  small  pieces  of 
wood.  They  were  connected  with  each  other,  the  posi- 
tive pole  of  each  with  the  negative  pole  of  the  following 
one,  and  dipped  in  diluted  vinegar.  Twenty  years  ago 
this  apparatus  had  great  success,  but  to-day  it  is  replaced 
by  others  more  perfect. 

In  all  these  voltaic  combinations  the  chemical  action  is 
the  same  as  in  Yolta's  battery.  The  zinc  becomes  oxy- 
dized  at  the  expense  of  the  water,  and  the  oxide  of  zinc 
combines  with  the  acid,  forming  a  nitrate,  an  acetate  of 
zinc,  etc.  The  hydrogen  of  the  water  is  given  off  upon 
the  negative  or  conducting  electrode. 

It  can  be  seen  without  going  any  farther  how  many 
different  batteries  may  be  conceived  by  simply  varying 
the  nature  of  the  electrodes  and  the  liquid.  But  many  of 
these  combinations  are  far  from  possessing  any  interest, 
and  our  remark  is  only  designed  to  call  the  attention  of 
the  reader  to  the  number  of  solutions  of  the  problem  of 
constructing  batteries. 


CHAPTER  VI. 
BATTERIES  WITHOUT  ACIDS. 

IN  addition  to  the  acids  there  are  numbers  of  liquids 
or  solutions  which  may  be  used  in  batteries,  a  few  of  which 
are  interesting. 

SEA-SALT  BATTERIES. 

On  account  of  the  facility  in  obtaining  chloride  of  so- 
dium, or  sea-salt,  or  common  salt,  it  is  often  made  use  of 
in  batteries.  The  battery,  whose  electrodes  are  carbon 
and  zinc,  is  almost  exclusively  used  in  Switzerland  for  tele- 
graph purposes,  with  dilute  sulphuric  acid,  or  more  fre- 
quently with  salted  water. 

There  are  several  dimensions  of  these.  The  smallest 
has  flat  electrodes  2f  inches  long ;  the  next  size  has  elec- 
trodes 4  inches  long  and  1J  inches  wide.  Both  sizes  have 
but  a  single  piece  of  carbon  in  each  cell.  The  first  can 
work  one  month,  the  second  three  months,  without  care. 

These  cells  certainly  cost  very  little,  and  there  is  scarce- 
ly any  consumption  of  the  zinc  while  the  circuit  is  open, 
although  the  zinc  is  not  amalgamated,  which  is  a  very 
satisfactory  condition.  The  electrodes  may  be  lifted  out 
during  the  suspension  of  work,  and  this  is  facilitated  by 
the  electrodes  being  attached  to  a  bar  of  wood.  By  lift- 
ing this  bar  the  electrodes  of  ten  cells  may  be  raised  at 
one  time. 

Another  model  of  this  same  battery  is  shown  in  Fig.  18. 


64  SINGLE-LIQUID  BATTEKIES. 

The  carbon  lias  the  form  of  a  hollow  cylinder,  in  tho 
centre  of  which  is  a  plate  of  zinc,  not  amalgamated,  as 
we  have  already  stated ;  these  two  electrodes  are  fastened 
to  a  strip  of  wood  which  rests  upon  the  rim  of  the  jar 
containing  salted  water.  The  comparatively  large  surface 
of  the  carbon  is  a  very  favorable  condition  (for  single- 
liquid  batteries),  as  we  explained  when  speaking  of  Wol- 
laston's  battery.  In  the  model  employed  on  Swiss  lines 
the  carbon  is  5^  inches  high,  and  has  an  exterior  diame- 
ter of  3£  inches.  These  batteries  can  do  service  from 
nine  to  twelve  months  without  requiring  attention. 

The  friend  to  whom  we  are  indebted  for  the  preceding 
information  uses  salt-water  batteries  for  domestic  bells. 
He  employs  cells  which  have  a  height  of  14  inches. 
Some  batteries  of  this  kind  have  been  known  to  work 
from  six  to  eight  years  without  any  care  whatever.  There 
is  one  which  worked  ten  years ;  the  zinc  had  of  course 
disappeared. 

Concerning  the  weakening  of  this  battery,  it  has  been 
found  that  it  may  be  exhausted  by  causing  a  constant 
current  of  a  short  circuit  to  pass  for  ten  or  twelve  hours, 
and  that  it  only  needs  two  or  three  hours  of  rest  to  regain 
its  lost  energy.  In  other  words,  depolarization  takes  place 
very  rapidly. 

The  sea-salt  battery  is  not  only  used  for  the  telegraph 
and  electric  bells,  but  for  electric  clocks. 

DUCHEMIN'S  ELECTRIC  BUOY. 

Duchemin  placed  elements  of  the  preceding  form 
directly  in  the  sea  by  attaching  them  to  scrme  floating 
body.  The  constant  agitation  of  water  caused  undoubt- 
edly an  almost  complete  depolarization.  Wh^rf  "several 


BATTEEIES   WITHOUT   ACIDS.  65 

cells  are  employed,  however,  they  are  in  the  same  liquid ; 
there  is  therefore  a  small  loss  of  electricity  ;  it  cannot  be 
of  much  consequence,  because  of  the  form  of  the  carbon 
which  surrounds  the  zinc.  A  perfect  insulation  of  the 
wires  connecting  the  cells  is  of  great  importance. 

The  main  object  of  these  batteries  was  the  preserva- 
tion of  sheets  of  iron  used  in  the  construction  of  vessels, 
barges,  buoys,  etc.  etc.  It  appears  that  the  hull  of  a 
vessel  undergoes  a  relatively  less  change  during  naviga- 
tion than  when  at  anchor  or  in  port ;  it  is  in  this  case 
that  the  use  of  Duchemin's  buoy  is  practicable.  These 
buoys  are  used  as  follows  : 

Seven  cells  about  4  inches  in  diameter,  for  instance, 
are  joined  in  intensity.  The  positive  pole  of  this  battery 
is  put  into  communication  with  the  sheets  of  iron  to  be 
preserved  ;  the  negative  pole  (that  is,  the  zinc  of  the  last 
cell)  is  in  the  sea,  as  indeed  are  the  others.  Under  these 
circumstances  it  has  been  proved,  by  experiments  made  at 
Cherbourg  by  officers  of  the  French  navy  appointed 
purposely  by  the  Minister  of  Marine,  that  a  surface  of 
iron  eighteen  times  larger  than  that  of  the  zinc  which 
forms  the  soluble  electrodes  of  the  battery  may  be  pre- 
served from  rust. 

It  appears  that  the  simple  addition  of  a  sheet  of  zinc 
is  not  sufficient  to  preserve  the  hull  of  an  iron  vessel 
from  rust,  but  it  can  be  done  by  means  of  one  or  seve- 
ral electric  buoys  ;  that  is  the  result,  at  least,  of  a  pro- 
longed experiment  on  a  small  iron  boat. 

These  interesting  experiments  were  unhappily  discon- 
tinued during  the  war  of  1870-71,  and  have  not  been  re- 
sumed. 

Before  leaving  the  subject,  we  will  say  that  there  is  a 
possible  superiority  of  sea-water  over  common  salted 


66  SINGLE-LIQUID  BATTERIES. 

water ;  for  sea- water  does  not  contain  chloride  of  sodium 
alone.  We  have  unfortunately  no  positive  information 
upon  this  point. 

The  salted-water  or  sea-water  battery,  although  inferior 
to  many  others  (especially  to  the  sal-ammoniac  battery,  of 
which  we  will  speak  later),  may  be  recommended,  above 
all,  in  places  near  the  sea,  where  the  expense  is  compara- 
tively small. 

ZINC-COPPER-SEA-WATER  BATTEEY. 

At  the  beginning  of  the  present  century  the  illustrious 
Sir  Humphry  Davy  proposed  to  protect  the  copper  hull 
of  vessels  by  means  of  a  sheet  of  zinc  (or,  indeed,  of  cast- 
iron)  put  into  communication  with  the  lining  and  im- 
mersed with  it  in  the  sea.  A  cell  was  thus  constructed 
in  which  the  zinc  (or  iron),  by  being  attacked,  protected 
the  copper. 

The  zinc  had,  of  course,  to  be  replaced  at  the  end  of  a 
certain  time ;  but  an  extent  of  active  zinc  surface  one 
hundred  and  fifty  times  larger  than  that  of  the  copper 
was  sufficient  to  protect  the  latter.  This  ingenious  idea 
had  to  be  abandoned  in  the  practice  for  the  following 
reason : 

The  zinc-copper  cell  of  which  we  have  spoken  gives 
off,  indeed,  hydrogen  upon  the  surface  of  the  copper ; 
but  at  the  same  time  it  decomposes  certain  salts  con- 
tained in  sea- water,  and  the  bases  (earthy  oxides — magne- 
sia and  lime)  deposit  themselves  upon  the  copper.  To 
this  crust  sea-grasses  and  shell-fish  attach  themselves  and 
slacken  to  a  great  extent  the  speed  of  the  vessel. 

In  the  absence  of  the  zinc  the  copper  is  slightly  at- 
tacked by  the  sea-water,  but  the  surface  remains  apparent- 


BATTERIES   WITHOUT   ACIDS.  C7 

ly  clean.  In  the  long-run  the  copper  is  used  up  ;  but  of 
two  evils  one  must  choose  the  less,  and  prefer  to  lose  a 
little  more  on  the  resale  of  old  linings  than  to  increase 
the  duration  of  voyages. 


ZINC-IRON-SEA-WATER  BATTERY. 

"Within  the  last  twenty  or  thirty  years  copper-lined 
vessels  have  gradually  been  abandoned  and  a  great  num- 
ber of  iron  ships  have  been  constructed.  Davy's  idea  is 
in  this  instance  applicable.  We  do  not  know  if  many  ex- 
periments have  been  made  or  not ;  but  the  result  of  one 
experiment  upon  a  French  frigate  showed  that  sheets  of 
metal  one  metre  square  lost  the  following  weights  after 
remaining  in  sea-water  one  month  : 

Grammes.  Grammes. 


Steel 28.10 

Iron 27.30 

Copper 3.80 

Lead only  traces. 


Zinc.... 5.60 

Galvanized  iron. ...     1.80 
Tin..  1.50 


These  figures  go  to  prove  that  iron  is  of  all  metals  the 
most  attacked  by  sea-water,  and  is  therefore  badly  chosen, 
as  far  as  preservation  is  concerned,  for  the  construction 
of  ships,  buoys,  etc. 

From  a  theoretical  point  of  view  there  would  be  a 
great  advantage  in  coppering  or  tanning  iron.  If  the 
iron  were  thoroughly  covered  with  a  thin  layer  of  cop- 
per or  tin  it  would  no  longer  be  in  contact  with  the  water, 
and  would  consequently  not  be  attacked.  But  a  small 
accident,  such  as  the  scraping  of  the  ship  on  a  sand-bar, 
for  instance,  might  be  enough  to  chip  off  a  little  piece  of 


68  SINGLE-LIQUID  BATTERIES. 

copper  or  tin,  when  the  exposed  iron  would  immediately 
be  attacked. 

Thus  would  be  established  an  iron-copper  or  iron-tin 
cell  which  would  excite  the  action  of  the  sea-water 
upon  the  iron.  It  might  indeed  go  so  far  as  to  make  a 
hole  in  the  iron.  It  will  be  seen  that  the  cell  thus  form- 
ed would  possess  peculiar  conditions  of  activity,  as  the 
negative  electrode  is  enormous  when  compared  with  the 
soluble  electrode  ;  and  besides,  the  constant  agitation  of 
the  wrater  would  tend  to  suppress  all  polarization. 

In  the  experiments  above  referred  to  the  surface  of  the 
sheets  of  metal  were,  of  course,  well  cleaned  before  each 
experiment. 

There  is  no  doubt  as  to  the  zinc  being  the  electro- 
positive element  of  the  zinc-sea-water-iron  battery,  and 
consequently  that  the  iron  is  electro-chemically  protected 
by  the  zinc. 

It  is  possible  that  the  feeble  electro-motive  force  of  this 
cell  may  be  insufficient  for  a  thorough  protection.  There 
may  also  be  some  accessory  action  which  might  make  the 
action  of  .the  cell  worse  than  simply  ineffectual,  as  in  the 
case  of  the  copper  linings. 

This  is,  we  think,  a  desirable  question  to  elucidate. 

ACCIDENTAL  REVERSING  OF  THE 
CURRENT. 

We  have  already  shown  how  a  voltaic  cell  may  be 
rendered  ineffective  by  electrolysis  of  the  salt  of  zinc  and 
the  deposit  of  zinc  upon  the  conducting  electrode. 

We  have  said  that  in  certain  cases  the  current  could  be 
reversed ;  this  phenomenon  was  observed  under  the  fol- 
lowing circumstances : 


BATTEEIES   WITHOUT   ACIDS.  69 

Certain  zinc-salt-water-carbon  batteries  that  had  been 
working  two  years  were,  by  accident,  short-circnited ; 
polarization  was  brought  to  its  maximum,  since  there 
was  no  resistance  in  the  external  circuit,  and  consequently 
the  intensity  was  the  greatest  it  could  be.  Soon  after 
the  battery  could  supply  almost  no  current  whatever; 
and  by  close  examination  it  was  found  that  in  one  out  of 
every  four  or  five  cells  the  poles  were  reversed ;  that  is, 
the  zinc  had  become  the  positive  pole,  and  the  carbon  the 
negative  pole.  There  was  present  a  polarization  similar 
to  that  which  would  have  taken  place  in  a  voltameter,  or 
in  a  secondary  battery  placed  in  the  circuit.  This  second- 
ary current  neutralized,  in  a  great  measure,  that  of  the 
other  cells  of  the  battery. 

In  this  singular  instance  the  polarization  of  certain 
elements  had  become  stronger  than  the  element  itself. 

It  is  easily  understood  that,  if  there  had  only  been  one 
cell  in  the  circuit,  this  reversing  of  the  poles  would  never 
have  taken  place ;  for  the  current  resulting  from  polari- 
zation is  necessarily  inferior  in  tension  or  electro-motive 
force  to  the  polarizing  current. 

One  more  remark  before  leaving  this  experiment.  If 
the  battery  cells  joined  in  intensity  were  and  would  re- 
main identical,  the  above  phenomenon  would  not  take 
place. 

If  twenty  cells  were  joined  in  intensity  and  in  short 
circuit  (that  is,  without  any  exterior  resistance),  the  in- 
tensity is  exactly  the  same  as  if  there  were  but  one  cell 
in  short  circuit ;  for  in  the  first  instance  the  electro-motive 
force  is  twenty  times  greater  and  the  resistance  of  the 
circuit  twenty  times  less  than  in  the  second  instance, 
which  establishes  an  exact  compensation. 

If  there  be  only  one  cell  in  the  circuit,  it  cannot  but 


70  SINGLE-LIQUID  BATTERIES. 

weaken,  and  no  reversing  of  the  poles  can  take  place. 
Therefore  in  a  battery  whose  cells  are  identical  there  can 
be  no  reversing.  For  the  occurrence  of  this  phenomenon 
the  cells  must  necessarily  be  dissimilar,  which  is  nearly 
always  the  case.  Some  are  polarized  from  the  beginning 
much  more  rapidly  than  others  ;  from  that  time  they  are 
no  longer  identical  cells,  and  the  poles  of  the  weaker 
ones,  which  are  the  most  polarized,  may  be  reversed. 

If  some  of  these  cells  should  accidentally  be  closed 
while  the  others  are  open,  they  become  rapidly  polarized ; 
the  cause  of  this  may  be  the  formation  of  climbing  saltr 
or  other  causes.  This  remark  shows  the  advantage  of 
the  careful  cleaning  of  batteries,  in  order  that  they  may 
work  regularly  and  for  a  long  time. 

We  will  return  to  this  subject  when  speaking  of  the 
sulphate-of -mercury  battery. 

CHEMICAL  ACTION  IN  SEA-SALT  BATTEEIES. 

No  one,  as  far  as  we  know,  has  analyzed  the  products 
formed  in  this  battery ;  it  must  be  a  very  complex  com- 
position, a  mixture  of  chloride  of  sodium  and  oxide  of 
zinc,  or  of  soda  and  zinc  chloride.  There  can  only  be 
conjectures  upon  this  subject,  as  no  analysis  has  been 
made.  The  only  known  fact  is  that  hydrogen  frees 
itself  from  the  carbon. 

These  analyses  are  probably  very  difficult,  and  the  com- 
binations formed  in  batteries  are  in  general  very  compli- 
cated ;  the  slowness  of  the  actions  favors  the  production 
of  bodies  more  complicated  than  those  of  which  mineral 
chemistry  generally  treats. 

Batteries  may  some  day  challenge  the  particular  atten- 
tion of  chemists,  who  will  find,  without  doubt,  that  they 


BATTERIES    WITHOUT  ACIDS.  71 

are  as  good  as  retorts  and  other  apparatus  used  in  labora- 
tories for  the  formation  of  composed  bodies,  of  which  a 
considerable  number  have  not  yet  been  studied.  We  are 
sure  that  chemistry  will  lose  nothing,  and  it  is  certain 
that  the  science  of  electricity  will  be  greatly  benefited 
by  this  study. 

The  difficulty  of  the  chemical  problem  presented  by 
the  sea-salt  battery,  and  indeed  by  nearly  all  batteries,  is 
increased  by  the  fact  that  the  nature  of  the  compositions 
formed  is  different  when  the  current  is  closed,  and  when 
it  is  open.  It  is  certain  that  if  there  were  a  change  in 
electric  conditions,  the  action  of  affinities  would  also 
change. 

Our  attention  will  again  be  called  to  this  subject,  when 
we  will  give  certain  reasons  supporting  the  above  sugges- 
tion. 

MARINE  BATTERIES. 

An  old  experiment  shows  that  if  a  plate  of  zinc  and  a 
plate  of  copper  be  immersed  in  the  sea  at  a  considerable 
distance  from  each  other  and  attached  to  a  single  con- 
ducting wire,  there  will  be  produced  in  this  wire  a  cur- 
rent of  considerable  intensity.  Whichever  way  it  may 
be  looked  at,  the  internal  resistance  of  this  battery  is  very 
feeble ;  either  by  considering  the  sea  as  the  jar  contain- 
ing the  liquid  and  the  two  electrodes ;  or,  adopting  recent 
views,  by  admitting  that  the  electricity  is  lost  in  the 
earth  (the  common  reservoir)  at  those  two  points  where 
the  line  touches  it.  This  combination  is  not  susceptible 
of  practical  application,  as  it  only  furnishes  one  cell  and 
not  a  multiple  battery ;  but  from  a  theoretical  point  of 
view  it  deserves  notice. 


72  SINGLE-LIQUID  BATTERIES. 


SAL-AMMONIAC  BATTERIES. 

By  substituting  a  solution  of  chloride  of  ammonium  or 
sal  ammoniac  for  the  liquids  previously  mentioned,  a  new 
series  of  batteries,  analogous  to  those  already  enumer- 
ated, may  be  realized.  We  will  call  the  reader's  atten- 
tion to  but  two  of  them,  wliich  possess  particular  interest. 

BAGRATION  BATTERY. 

The  electrodes  of  this  battery  are  the  zinc  and  the 
copper;  they  are  immersed  in  a  jar  filled  with  earth 
sprinkled  with  sal  ammoniac.  "  It  produces  a  wonder- 
fully constant  current  which  is  the  result  either  of  the 
reduction  of  the  hydrogen  upon  the  copper  by  the  com- 
position formed  there  by  the  sal  ammoniac,  or  of  the 
absorption  of  the  hydrogen  by  the  earth  itself,  which 
indeed  acts  as  a  diaphragm.  It  is  best  not  to  put  the 
two  plates  of  the  cell  too  near  to  each  other,  and  to  im- 
merse the  plate  of  copper,  before  putting  it  in  the  earth, 
in  a  solution  of  sal  ammoniac,  leaving  it  to  dry  until  a 
greenish  layer  is  formed  upon  its  surface."  * 

In  spite  of  these  precautions,  this  battery  has  been  put 
aside ;  but  it  is  possible  that  it  may  again  be  taken  up. 

CARBON-ELECTRODE  BATTERY. 

This  battery  differs  from  the  preceding  one  in  the 
substitution  of  carbon  for  copper.  We  have  already 
explained  the  advantages  of  carbon. 

To  give  to  these  batteries  their  maximun  force,  and  to 

*  De  La  Rive,  Traite  d'filectricite. 


BATTERIES   WITHOUT  ACIDS.  73 

render  polarization  as  slow  as  possible,  they  are  arranged 
as  follows : 

The  carbon  electrode  is  placed  in  a  porous  porcelain 
jar,  which  is  then  filled  up  with  small  pieces  of  carbon ; 
a  considerable  extent  of  surface  is  thus  given  to  the  nega- 
tive electrode.  This  porous  jar  is  then  placed  in  a  glass 
or  stoneware  jar  which  contains  the  solution  of  sal  am- 
moniac. The  zinc  is  immersed  in  the  liquid ;  it  has  the 
form  of  a  hollow  cylinder,  and  a  thickness  of  ^  of  an 
inch  is  sufficient,  as  there  is  but  little  waste. 

This  battery  presents  an  important  advantage,  only 
found  thus  far  in  the  Bagration  battery  and  in  the  sea- 
salt  battery. 

All  batteries,  indeed,  in  which  the  positive  or  soluble 
electrode  is  zinc  in  sal  ammoniac  have  the  same  advan- 
tages. 

As  long  as  the  circuit  is  open  there  is  no  chemical 
work  going  on  ;  the  action  of  the  sal  ammoniac  upon  the 
zinc  does  not  commence  until  the  circuit  is  closed,  and 
ceases  immediately  upon  the  reopening  of  the  circuit. 
In  order  to  make  this  important  point  perfectly  clear, 
the  following  experiment  must  be  made :  Place  an  ordi- 
nary piece  of  zinc  in  a  solution  of  sal  ammoniac  and  leave 
it  there  for  some  time,  several  weeks  for  instance,  when 
it  will  be  seen  that  the  zinc  is  not  attacked  in  the  slightest 
degree.  If  now  a  fragment  of  metal,  iron,  or  copper,  or 
even  a  piece  of  carbon,  be  added  in  the  jar,  it  is  soon  seen 
that  the  zinc  is  attacked  and  a  white  salt  is  formed. 

It  is  thus  seen  that  for  the  attack  of  sal  ammoniac 
upon  the  zinc  the  formation  of  a  cell  is  necessary ;  if  the 
zinc  does  not  touch  the  metal  added,  no  attack  takes 
place. 

We  will  not  insist  upon  the  many  consequences  of  this 


74  SINGLE-LIQUID  BATTERIES. 

simple  experiment,  but  the  plain  result  is,  that,  in  bat- 
teries formed  with  zinc  immersed  in  a  solution  of  sal 
ammoniac,  there  is  no  chemical  action  except  when  the 
battery  is  doing  useful  work. 

From  a  practical  point  of  view  this  advantage  of  sal- 
ammoniac  batteries  is  capital,  for  in  most  applications 
batteries  only  work  at  intervals.  In  the  principal  tele- 
graph offices,  where  the  greatest  number  of  telegrams 
are  sent  and  received,  only  intermittent  currents  are 
used,  but  in  such  quantities  that  an  almost  constant 
demand  for  electric  current  is  imposed  upon  the  battery ; 
but  in  branch  offices  there  are  generally  long  intervals 
between  telegrams,  and  there  is  most  frequently  no  service 
at  all  during  the  night. 

In  the  application  of  domestic  bells,  the  battery  should 
always  be  ready  for  vrork  night  and  day ;  the  current  is 
consequently  used,  on  an  average,  but  a  few  minutes  in  the 
twenty-four  hours.  In  applications  of  this  kind  it  is  seen 
that  the  period  during  which  the  batteries  remain  in- 
active is  a  hundred  times,  nay,  twro  hundred  times,  longer 
than  that  during  which  they  work,  and  that  the  economy 
should  therefore  be  made  during  the  time  in  which  no 
current  is  required. 

"We  will  add  that,  such  as  it  is,  it  could  be  very  well 
used  for  electric  bells,  and  could,  if  necessary,  serve  in 
a  branch  telegraph  office.  The  battery  in  question  has 
indeed  but  one  fault:  it  becomes  polarized  when  fur- 
nishing a  current.  However,  for  such  an  intermittent  ser- 
vice this  inconvenience  disappears;  for  during  its  short 
period  of  work,  polarization  is  barely  perceptible,  and  it 
has  sufficient  time  to  disappear  completely  during  the 
long  intervals  of  rest.  To  M.  Leclanche  is  due  the  dis- 
covery of  the  advantages  presented  by  the  sal-ammoniac 


BATTERIES   WITHOUT   ACIDS.  75 

battery.  He  first  established  the  fact  that  a  battery 
could  be  produced  in  which  the  waste  did  not  exceed,  in 
proportion,  the  electricity  supplied. 

Another  advantage  of  this  battery  is  that  if,  at  a  cer- 
tain time,  it  is  seen  to  weaken  and  there  be  no  sal  ammo- 
niac at  hand,  it  can  be  charged  for  the  time  being  with 
common  salt.  But  this  means  should  only  be  resorted  to 
in  an  emergency,  as  the  current  obtained  with  common 
salt  is  less  intense  than  that  furnished  by  sal  ammoniac. 

ACTION  OF  AIE  UPON  THE  PRECEDING 
BATTERY. 

From  various  experiments  made  with  carbon-electrode 
and  sal-ammoniac  batteries  the  following  conclusions 
may  be  drawn : 

1.  The  surface  of  the  carbon  should  be  as  large  as  pos- 
sible compared  to  that  of  the  zinc ;  and  by  increasing  the 
mass  of  carbon  according  to  a  given  quantity  of  zinc, 
polarization  may  be  suppressed. 

2.  A  part  of  the  carbon,  should  be  exposed  to  the  air; 
for  it  has  been  proved  that  when  the  carbon  is  totally 
immersed    the  intensity  is  diminished,  but  recovers  as 
soon  as  some  of  the  liquid  has  been  taken  out.-    This  is 
what  a  French  physicist  calls  letting  the  carbon  breathe. 
The  use  of  porous  jars  which  overreach  the  top  of  the 
glass  jar  is  very  important. 

3.  Preference  should  be  given  to  gas-retort  carbon,  on 
account  of  its  porosity,  and,  as  we  said  in  speaking  of  the 
chemical  action  in  Yolta's  battery,  it  must  be  used  in 
fragments  large  enough  to  permit  the  access  of  air.     The 
powdered  cake,  formerly  used,  should  be  discarded. 

These   conclusions  will   be   readily   admitted   by   the 


76  SINGLE-LIQUID  BATTEEIE9. 

• 

reader,  who  can  understand  that  the  presence  of  oxygen 
in  the  pores  of  the  carbon  contributes  to  the  depolariza- 
tion of  the  battery.  It  is  possible  that  the  particular  fac- 
ulty of  the  carbon  for  absorbing  gases  in  large  quantities 
here  plays  some  part,  and  that  the  properties  of  the  gases 
thus  condensed  in  the  pores  of  the  carbon  may  be  dif- 
ferent from  what  they  are  under  ordinary  circumstances. 

CHEMICAL  ACTION  IN  SAL-AMMONIAC 
BATTEKIES. 

A  French  chemist,  in  analyzing  crystals  formed  in  sal- 
ammoniac  batteries,  found  this  formula  for  them  : 

3ZnCl,     4NH3,     4110. 


The  gases  given  off  from  the  element  were  found 
to  be: 

•J  volume  of  hydrogen. 

•J          "          nitrogen  and  carbonic  acid. 

-J-          "          heavy  carburet  ted  hydrogen. 

These  results  only  confirm  that  which  we  have  said 
above  of  the  complicated  composition  of  bodies  formed 
in  batteries. 


OTHER  BATTERIES. 
ZINC-IEON-WATER  BATTEKY. 

We  have  already  spoken,  several  times,  of  batteries  in 
which  the  electrodes  were  zinc  and  iron ;  and  we  have 
seen  that  the  zinc  was  always  the  generating  electrode, 
and  the  iron  the  conducting  electrode. 


OTHER  BATTERIES.  77 

Every  one  knows  that  to  protect  iron  from  rust  it  is 
covered  with  zinc,  and  is  then  generally  known  under  the 
name  of  galvanized  iron. 

If  the  galvanized  iron  be  exposed  to  rain  or  humidity, 
the  uncovered  parts  of  the  iron  constitute  a  cell  with  the 
zinc,  and  the  iron  is  protected  by  the  zinc.  This  electro- 
chemical protection  increases  considerably  the  impor- 
tance of  the  process  of  galvanizing  iron. 

It  must  be  said  that  the  oxide  of  zinc  produced  by  the 
exposure  of  the  zinc  to  the  air  is  insoluble  in  water,  and 
forms  a  protecting  layer  which  hinders  further  oxidation ; 
that  is  the  principal  reason  for  the  use  of  zinc  in  out-door 
works  alone  or  with  iron. 


IKON-TIN  BATTEKY. 

It  is  interesting  to  examine,  from  the  same  stand-point, 
tinned  iron.  Tin  is  liable  to  but  very  little,  alteration 
in  water  or  when  exposed  to  damp  air.  For  many  years 
it  has  been  *the  practice  to  tin  iron,  by  which  its  dura- 
bility is  greatly  increased. 

It  is  important  to  note  that  if  the  iron  be  exposed  at 
any  point  it  is  promptly  attacked,  because  in  the  voltaic 
cell  formed  with  water,  or  simply  damp  air,  the  iron  is 
the  generating  electrode.  Under  these  circumstances  the 
rust  is  seen  to  advance  step  by  step,  and  to  lift  up  and 
undermine  the  protecting  layer  of  tin.  This  metal  pro- 
tects only  the  part  it  covers,  but  it  renders  the  iron  more 
liable  to  rapid  rust  than  if  it  were  not  there. 


78  SINGLE-LIQUID  BATTEEIES. 


ALUM  BATTEEY. 

Alum  or  potassio-aluminic  sulphate  (KA13  4SO4)  is 
employed  in  several  branches  of  industry. 

A  German  physicist  arranged  a  battery  whose  elec- 
trodes were  ordinary  zinc  and  carbon,  and  whose  liquid 
was  a  solution  of  alum ;  this  battery  undergoes  polariza- 
tion, of  course,  but  it  is  said  to  depolarize  after  the  circuit 
has  been  open  but  a  very  short  time. 

The  chemical  action  must  be  very  complicated  in  this 
battery.  When  the  already  complex  nature  of  the  alum 
is  taken  into  consideration,  the  addition  of  the  zinc  can- 
not but  lead  one  to  believe  that  the  composition  thus  pro- 
duced is  extremely  complicated. 

At  Mulhouse  they  use  for  electric-clock  purposes  a 
battery  whose  liquid  is  a  mixture  of  sea-salt  (500  grammes) 
and  pulverized  alum  (200  grammes)  dissolved  in  water. 
This  application  deserves  notice,  as  constant  batteries  are 
generally  thought  to  be  necessary  for  the  service  of  elec- 
tric clocks. 

The  cells  of  the  above  battery  are  very  large  :  the  hol- 
low carbon  cylinder  has  an  exterior  diameter  of  4J  inches 
and  an  interior  diameter  of  3J  inches  ;  the  plate  of  zinc 
is  2f  inches  wide,  and  these  two  electrodes  are  immersed 
about  10  inches  in  the  liquid.  There  are  twenty  clocks 
distributed  in  two  distinct  circuits ;  there  are  two  clos- 
ings of  the  circuit  a  minute,  each  lasting  one  second. 
There  are  sixteen  cells,  of  which  two  are  charged  every 
week  in  order  to  always  keep  the  battery  the  same ;  each 
cell  works,  therefore,  four  months  without  any  attention 
whatever. 

Another  step  in    advance  has  been  made  in  the  ar- 


OTHER   BATTERIES.  79 

rangement  of  a  battery  which  is  only  renewed  once  in 
every  two  years  ;  it  is,  however,  only  used  in  the  fire- 
telegraph  service,  which  demands  but  little  work. 

These  practical  examples  show  once  more  that  if  the 
use  of  single-liquid  batteries  is  well  understood,  they  can 
be  employed  in  many  instances. 

KEMAEKS   UPON   SINGLE-LIQUID   BAT- 
TEEIES. 

It  might  be  generally  said  that  by  taking  any  two 
pieces  of  different  metals,  or  a  piece  of  metal  and  a  piece 
of  carbon,  and  immersing  them  in  some  liquid  conductor 
of  electricity,  a  battery  could  be  made. 

The  more  lively  the  action  of  the  liquid  upon  the  posi- 
tive electrode  (negative  pole),  the  greater  intensity  the 
battery  will  possess ;  there  will  be  no  action  upon  the 
other  electrodes,  at  least  not  during  the  passage  of  the 
current ;  that  is,  not  while  the  exterior  circuit  is  closed. 
The  choice  of  this  second  electrode  is,  however,  far  from 
being  a  thing  of  indifference ;  the  less  the  electrode  is 
capable  of  being  attacked  by  the  liquid,  the  greater  will 
be  the  intensity  of  the  battery.  That  is  the  reason  why 
platinum  and  carbon  should  be  preferred,  at  least  with 
sulphuric  acid,  nitric  acid,  and  the  other  liquids  of  which 
we  have  spoken. 

The  electric  action  is  the  result,  in  reality,  of  the  dif- 
ference of  two  chemical  actions,  one  of  which  takes  place 
while  the  other  is  prevented ;  one  of  the  electrodes  is 
attacked,  the  other  is  preserved  from  the  attack  of  the 
liquid  (at  least  while  the  circuit  is  closed). 

The  more  energetic  the  action  upon  the  positive  elec- 
trode and  the  less  this  action  upon  the  negative  electrode, 


80  SINGLE-LIQUID  BATTERIES. 

the  more  developed  will  be  the  electric  phenomenon.  For 
instance,  a  zinc-acidulated  water-iron  battery  has  but  little 
power ;  the  action  of  the  liquid  upon  both  electrodes  is 
very  lively  as  long  as  the  circuit  is  open  ;  as  soon  as  it  is 
closed  the  action  upon  the  iron  is  stopped ;  but  it  reacts 
upon  the  attack  of  the  zinc  and  diminishes  it.  If  plati- 
num be  substituted  for  iron,  the  zinc  alone  is  acted  upon 
and  the  platinum  remains  unattacked  before  the  circuit 
is  closed;  when  the  circuit  is  closed  and  the  current 
flows,  the  action  upon  the  zinc  is  hardly  diminished. 

Many  persons  have  proposed  compound  liquids :  mix- 
tures of  sulphuric  acid  and  sea-salt,  mixtures  of  salted 
water  and  flower  of  sulphur,  etc.  Satisfactory  results  may 
possibly  be  obtained  in  this  manner ;  but  this  study  has 
lost  a  great  deal  of  interest  on  account  of  the  invention 
of  constant  batteries,  of  which  we  will  now  speak. 


PAET  II. 
TWO-LIQUID  BATTERIES. 


rNTRODUCTIOK 

liave  already  said  that  in  order  to  successfully 
oppose  polarization  of  electrodes,  chemical  substances 
capable  of  absorbing  the  hydrogen  as  it  is  given  off  upon 
the  negative  electrode  must  be  employed.  A  second 
liquid  is  most  frequently  used  for  this  purpose ;  nitric 
acid  is  eminently  suitable  for  this  office. 

Experiment. — Let  us  take  a  zinc-sulphuric-acid-plati- 
num battery ;  cause  the  current  it  furnishes  to  pass  in  a 
galvanometer.  The  deflection  of  the  galvanometric 
needle  is  seen  to  decrease,  and  thus  mark  the  progress  of 
polarization.  Let  us  now  throw  a  few  drops  of  nitric  acid 
around  the  platinum,  and  the  intensity  of  the  current 
will  be  seen  to  increase  immediately,  thus  making  mani- 
fest a  decrease  in  the  polarization.  It  is  easily  understood 
that  the  nitric  acid  is  decomposed  by  its  contact  with  the 
hydrogen  ;  water  and  bioxide  of  nitrogen  are  formed,  the 
freeing  of  which  produces,  at  the  contact  with  the  air, 
nitric-tetroxide  vapors,  very  sensible  to  the  smell. 

In  order  to  use  nitric  acid  most  advantageously,  it 
should  not  be  spread  throughout  the  whole  mass  of  the 


82  TWO-LIQUID  BATTERIES. 

liquid,  but  should  be  concentrated  around  the  electrode 
to  be  polarized.  To  fulfil  this  condition  porous  jars  have 
been  adopted  to  separate  the  two  liquids,  one  of  which  is 
designed  to  dissolve  the  zinc  and  the  other  to  dissolve  the 
hydrogen  given  off,  or  on  the  point  of  being  given  off, 
upon  the  negative  electrode. 

The  denomination  "  two-liquid  battery"  is  badly  chosen, 
because  in  many  instances,  which  we  will  cite,  solids  are 
used  as  depolarizing  agents  instead  of  liquids ;  it  would 
have  been  more  exact  to  say  two-electrolyte  battery,  but 
as  this  appellation  is  not  in  use,  we  do  not  think  best  to 
adopi^  it.  •  „ 

In  most  cases  chemical  depolarization  is  obtained  by 
means  of  substances  capable  of  furnishing  oxygen,  which, 
combining  with  the  -oxygen,  prevent  the  latter  from  free- 
ing itself  and  polarizing  the  negative  electrode. 

In  the  experiment  that  we  have  described  above,  the 
nitric  acid,  being  decomposed,  produces  oxygen,  and  hence 
the  result.  IS'itric  acid  NO5,  being  very  rich  ir.  oxygen 
and  easily  decomposed,  was  naturally  fixed  upon ;  it  is 
one  of  the  best  batteries  known. 

Other  acids  besides  nitric  acid  could  be  used :  chloric 
acid  C1O5,  chromic  acid  CrO3,  permanganate  acid 
Mn2O7  are  indicated  ;  but  they  are  not  generally  used  in 
this  way. 

Salts  (chlorate  of  potash,  bichromate  of  potash,  etc.)  are 
generally  substituted,  which  give  off  oxygen  under  the 
influence  of  the  sulphuric  acid. 

It  may  be  said,  in  a  general  way,  that  all  means  of  pro- 
ducing oxygen  can  be  satisfactorily  employed  for  the  de- 
polarization of  the  negative  electrode  of  a  cell. 

Oxides  from  which  oxygen  is  readily  freed  might  be 
employed  instead  of  acids ;  oxygenized  water  would  be 


INTRODUCTION.  83 

excellent  if  the  difficulty  in  preparing  and  preserving  it 
did  not  render  it  practically  impossible ;  but  the  bioxide 
of  manganese  and  the  bioxide  of  lead  may  be  used,  as 
will  be  seen  farther  on. 

We  have  said  how  that  acids  rich  in  oxygen  were  not 
used  alone  ;  they  are  generally  in  the  shape  of  some  salt 
from  which  they  are  freed  by  sulphuric  acid,  or,  if  need 
be,  by  some  other.  In  the  same  manner,  the  combination 
of  peroxides  and  sulphuric  acid  may  be  employed  to  give 
off  oxygen. 

All  the  processes  which  we  have  just  described  con- 
sist in  the  use  of  oxidizing  bodies  or  oxidizing  mixtures ; 
there  is  one  more  kind  to  be  indicated ;  namely,  the  use 
of  chlorine,  which  is  also  an  oxidant  in  the  presence  of 
water,  because  it  tends  to  combine  with  the  hydrogen 
and  to  free  the  oxygen. 

All  the  means  for  producing  chlorine  may  be  used  for 
depolarization. 

We  have  yet  to  speak  of  a  chemical  means  of  depo- 
larization very  different  from  any  that  we  have  hitherto 
mentioned,  and  which  according  to  many  is  the  best.  It 
consists  in  the  use  of  salts,  such  as  sulphate  of  copper, 
which  decompose  under  the  influence  of  the  current, 
depositing  their  metal  and  checking  the  freeing  of 
hydrogen.  The  result  is  that  a  metal  is  deposited  upon 
the  negative  electrode  instead  of  gaseous  hydrogen ;  if, 
at  the  start,  the  electrode  was  of  copper,  its  surface  would 
remain  unchanged,  and  consequently  there  is  no  polariza- 
tion. 

We  will  examine  in  detail  all  these  means  of  depolari- 
zation and  indicate  the  most  important  applications  that 
have  been  made,  always  following  the  same  method  that 
we  employed  in  the  study  of  single-liquid  batteries. 


84  TWO-LIQUID   BATTERIES. 

The  first  idea  upon  the  processes  which  we  have  just 
mentioned  dates  from  the  year  1829,  and  is  found  in  a 
memoir  of  Becquerel. 

"It  should  be  observed,"  says  Becquerel,  "that  the 
battery  carries  in  itself  the  cause  of  the  continual  diminu- 
tions in  the  intensity  of  the  electric  current ;  for  as  soon 
as  it  begins  to  work,  there  take  place  decompositions  and 
transportations  which  polarize  the  plates  in  such  a  man- 
ner as  to  produce  currents  contrary  to  the  first  one.  The 
art  consists,  therefore,  in  dissolving  these  deposits,  as  they 
form,  by  means  of  properly  placed  liquids.  .  .  .  This 
is  attained  by  means  of  the  process  that  I  have  de- 
scribed. .  .  .  By  thus  diminishing  the  intensity  of 
the  secondary  current,  sensibly  constant  effects  may  be 
obtained." 

It  is  this  view,  so  plainly  expressed  fifty  years  ago, 
that  has  suggested  the  present  work  and  which  justifies 
the  classification  that  we  have  adopted. 

The  first  indication  of  a  battery  depolarized  by  means 
of  a  salt  of  the  metal  which  constitutes  the  conducting 
electrode  is  found  in  the  following  words  taken  from 
BecquereFs  memoir : 

"  Let  us  continue  to  use  saturated  solutions  of  metallic 
salts,  which  cause  no  decomposition  of  the  .immersed 
metal.  Let  us  then  put  with  the  copper  a  saturated 
solution  of  nitrate  of  copper,  and  with  the  zinc  a  satu- 
rated solution  of  sulphate  of  zinc.  The  deflection  of  the 
galvanometric  needle  will  reach  88°  and  then  undergo 
but  a  slow  diminution.  An  addition  of  nitric  acid  to  the 
solution  of  nitrate  does  not  modify  the  intensity  of  the 
current.  The  result  is  the  same  when  sulphuric  acid  is 
added  in  the  solution  of  sulphate,  the  zinc  having  been 
well  cleaned.  Here  is  then  a  maximum  effect." 


INTRODUCTION.  85 

Finally,  Becqnerel  speaks  of  depolarization  obtained 
by  means  of  nitric  acid  ;  he  experiments  upon  a  cell  con- 
taining zinc,  copper,  and  a  porous  partition,  the  common 
liquid,  being  a  saturated  solution  of  sulphate  of  zinc.  He 
says : 

"  According  to  the  general  rule  the  zinc  ought  to  be 
more  attacked  than  the  copper,  and  such  is  the  result ; 
the  deflection  is  then  62°,  and  if  a  few  drops  of  nitric 
acid  be  added  in  the  compartment  containing  the  copper 
plate,  where  the  chemical  action  is  most  feeble,  the  gal- 
vanometric  needle  will  mark  86°  and  will  remain  station- 
ary for  some  time.  .  .  .  The  same  quantity  of  acid 
put  with  the  zinc  will  sensibly  diminish  the  intensity  of 
the  current."  A  little  farther  on  he  says :  u  I  once  suc- 
ceeded in  obtaining  a  compensation,  so  that  the  needle's 
deflections  remained  constant  during  one  hour,  an  advan- 
tage never  found  in  ordinary  batteries." 

The  only  thing  that  escaped  Becquerel's  notice  is  the 
part  that  the  hydrogen  plays  in  polarization ;  he  did  not 
observe  the  nature  of  the  chemical  reactions  whteh  take 
place  in  those  batteries  now  termed  Danieli's  battery  and 
Grove's  battery.  He  studied  batteries  from  a  purely 
physical  stand-point  and  neglected  the  chemical  problem. 


CHAPTER  I. 
DANIELL'S  BATTERY. 

IN  a  first  series  we  will  put  all  the  batteries  in  which 
depolarization  is  effected  by  the  use  of  salts.  In  order 
to  facilitate  our  exposition,  we  ought  to  divide  this  series 
into  several  categories,  that  of  sulphates,  that  of  chlo- 
rides, etc.  In  fact,  the  two  that  we  have  just  men- 
tioned are  the  only  ones  which  possess  any  importance 
up  to  the  present  date. 

DESCKIPTIOK 

As  we  are  not  paying  any  attention  to  the  chronologi- 
cal order  of  discoveries,  we  will  not  describe  the  battery 


FIG.  21 


of  Daniell  under  the  form  given  to  it  by  its  inventor  in 
1836 ;  the  form  which  we  give  is  that  in  present  use. 
Fig.  21    represents   three  cells  joined  in  intensity.    In 


DANIELL'S   BATTERY.  87 

each  are  seen  the  outside  glass  jar,  a  thin  hollow  cylinder 
of  zinc,  z,  a  porcelain  porous  jar,  and  a  strip  of  copper,  c. 

The  two  liquids — a  saturated  solution  of  sulphate  of 
copper  in  the  porous  jar  and  dilute  sulphuric  acid  in  the 
outside  jar — are  separated,  but  communicate  with  each 
other  through  the  pores  of  the  porcelain  jar.  The  cop- 
per electrode  is  immersed  in  the  sulphate,  and  the  zinc  in 
the  acidulated  water. 

The  only  difference  between  this  battery  and  that  of 
Yolta  is  the  addition  of  sulphate  of  copper  around  the 
copper  electrode.  The  zinc  dissolves,  oxidizing  and  form- 
ing sulphate  of  zinc.  The  hydrogen  produced  by  this 
reaction,  instead  of  being  given  off  upon  the  negative 
electrode,  takes  the  place  in  the  sulphate  of  copper  of  an 
equivalent  quantity  of  copper,  which  is  deposited  upon 
the  electrode.  This  deposit  not  changing  chemically  the 
surface  of  the  electrode,  it  is  plain  that  there  is  nothing 
like  polarization  produced.  In  other  words,  the  addition 
of  sulphate  of  copper  is  sufficient  to  completely  depolar- 
ize the  negative  or  conducting  electrode. 

Such  is  the  simple  combination  due.  to  Darnell,  the 
most  perfect  as  yet  invented. 

If  the  action  of  the  battery  continues  for  some  time, 
all  the  sulphuric  acid  in  the  outside  jar  will  be  converted 
into  sulphate  of  zinc ;  the  action,  however,  is  not  in  the 
least  checked  by  this,  and  the  electro-motive  force  re- 
mains almost  the  same.  The  chemical  action  that  then 
takes  place  consists  in  the  substitution  of  zinc  for  the 
copper  in  the  sulphate  of  copper,  and  the  progressive 
transformation  of  sulphate  of  copper  into  sulphate  of 
zinc. 

In  general  practice  the  battery  is  not  charged  with  di- 
lute sulphuric  acid ;  neither  is  any  sulphate  of  zinc  put 


88  TWO-LIQUID   BATTEKIES. 

in  the  outside  jar,  but  simply  pure  water.  At  first  the 
action  is  more- feeble,  and  the  internal  resistance  of  the 
cell  much  greater;  but  the  sulphate  of  copper,  which 
traverses  the  porous  partition,  is  transformed  into  sulphate 
of  zinc  by  the  action  of  the  zinc,  and  the  pure  water  is 
soon  found  to  contain  a  certain  proportion  of  salt,  by 
which  its  conductivity  is  increased.  This  first  period 
lasts  a  longer  or  shorter  time,  according  to  the  circum- 
stances ;  but  a  very  effectual  way  of  shortening  it  consists 
in  closing  the  circuit  with  a  very  short  conductor,  which 
has  no  resistance ;  the  chemical  action  is  thus  made  more 
lively,  and  at  the  end  of  an  hour  or  two  the  battery  may 
be  said  to  have  reached  its  normal  state  of  work. 

Electro-motive  Force. — As  this  battery  is  not  polarized, 
its  electro-motive  force  ought  to  be  invariable ;  in  fact,  the 
two  expressions  are  synonymous. 

The  experiment  shows  that  the  electro-motive  force  of 
DanielPs  battery  is  indeed  very  constant.  In  the  prac- 
tice it  may  be  taken  as  a  unit,  and  others  can  be  compared 
with  it. 

The  British  Association  has  adopted  a  unit  differing 
very  little  from  this  one,  and  has  given  to  it  the  name  of 
Yolt.  The  cell,  in  which  the  electro-motive  force  is  ex- 
actly equal  to  the  volt,  differs  but  slightly  from  that  of 
Daniell.  It  is  a  cell  in  which  the  copper  is  immersed  in 
a  solution  of  nitrate  of  copper,  and  the  zinc  amalgamated 
in  sulphuric  acid  diluted  with  twelve  times  its  weight  of 
water. 

The  electro-motive  force  of  Daniell's  cell  is,  we  said, 
very  constant,  and  it  varies  but  slightly  with  the  tempera- 
ture. 

It  has  been  found  that  if  it  is  1000  at  18°  centigrade, 
it  will  only  reach  1015  at  100°  centigrade.  It  changes 


DANIELL'S  BATTERY.  89 

very  little  with  the  acidity  of  the  liquid.  If  it  is  1079 
with  acid  diluted  with  four  times  its  weight  of  water,  it 
only  diminishes  to  0.978  with  acid  diluted  with  twelve 
times  its  weight  of  water.  The  richness  of  a  solution  of 
sulphate  of  copper  has  but  little  influence  upon  it. 

M.  Regnauld  has  given  the  following  figures  concern- 
ing a  cell  without  sulphuric  acid  and  charged  with  solu- 
tions of  sulphate  of  zinc  and  sulphate  of  copper : 

Solution  saturated  with  sulphate  of  copper 175 

The  same,  diluted  with  twice  its  bulk  of  water 175 

The  same,  diluted  with  ten  times  its  bulk  of  water. 174 

The  same,  diluted  with  fifty  times  its  bulk  of  water 172 

These  numbers  are  not  expressed  in  volts,  but  a  unit 
was  taken  which  is  equal  to  the  electro-motive  force  of  a 
bismuth-copper  thermo-electric  cell  whose  solderings  are 
0°  and  100°. 

The  electro-motive  force  of  a  Daniell  cell  with  sulphu- 
ric acid  and  a  saturated  solution  of  sulphate  of  copper  is 
equal  to  179  of  the  above  units.  It  is  therefore  seen 
that  the  substitution  of  sulphate  of  zinc  for  dilute  sul- 
phuric acid  does  not  notably  change  the  electro-motive 
force. 

We  have  said  that  it  did  not  vary  wTith  the  richness  of 
the  solution  of  sulphate  of  zinc ;  it  has  been  shown  that 
there  is  no  perceptible  change  when  the  solution  is  at 
first  concentrated  and  then  diluted  with  one  hundred  times 
its  bulk  of  water.  The  thickness  or  nature  of  the  porous 
jar  has  no  influence;  porous  partitions  of  many  kinds 
have  been  tried,  such  as  gold-beaters'  skin,  pipe-clay, 
under-baked  porcelain,  tubes  of  rosewood  and  of  the 
pear-tree,  of  ebony  and  of  boxwood. 

Resistance. — It  must,  however,  be  acknowledged  that 


90  TWO-LIQUID  BATTERIES. 

the  condition  and  force  of  a  battery  are  always  variable ; 
for  if  at  the  start  the  solution  is  too  weak,  it  becomes 
more  and  more  concentrated,  and  its  conductivity  is  con- 
stantly changing.  The  following  figures  show  that  it 
reaches  a  maximum  and  then  decreases  : 

Solution  concentrated  with  sulphate  of  zinc  (specific  gravity 

1.441) 5.77 

The  same,  diluted  with  its  bulk  of  water 7. 13 

The  same,  diluted  with  three  times  its  bulk  of  water 5.43* 

The  conductivity  of  liquids  varies  also  with  the  tem- 
perature;  that  of  a  solution  of  sulphate  of  zinc  reaches 
its  maximum  at  14°  cent. 

If  the  nature  of  the  liquid  in  the  outside  jar  changes, 
that  in  the  porous  jar  will  also  change.  In  fact,  the  solu- 
tion of  sulphate  of  copper  gradually  weakens,  and  its  con- 
ductivity changes  with  its  state  of  concentration  and  the 
temperature. 

A  few  crystals  of  sulphate  of  copper  may  be  added  in 
the  porous  jar  to  keep  up  the  solution.  The  more  con- 
centrated the  solution  becomes  the  heavier  it  gets,  and 
in  order  to  keep  it  in  a  state  of  saturation  up  to  the  top 
of  the  jar,  they  used  to  suspend  crystals  to  the  upper  part 
by  means  of  a  small  diaphragm  of  copper  soldered  to  the 
strip  of  copper ;  but  this  precaution  has  been  generally 
abandoned,  and  the  crystals  are  now  simply  thrown  in 
the  bottom  of  the  jar.  This  suppression  causes  no  incon- 
veniences, because  the  battery  loses  none  of  its  qualities 
wrhen  the  liquid  ceases  to  be  saturated ;  it  is  indeed 
an  advantage,  for  the  consumption  of  sulphate  is  less 
active. 

A  saturated  solution  of  sulphate  of  copper  has,  how- 

*  See  table  3,  end  of  volume. 


DANIELL'S  BATTERY.  91 

ever,  a  greater  conductivity  than  when  it  is  diluted  with 
water,  as  the  following  table  shows : 

Sulphate  of  copper.     Saturated  solution  (specific  gravity  1.171)    5.43 

The  same,  diluted  to  half 3.47 

The  same,  diluted  to  quarter 2.08 

It  should  therefore  be  admitted  that  the  use  of  a 
diluted  solution  increases  the  resistance  of  the  battery ; 
but  it  is  probable  that  the  sulphate  of  zinc  in  mixing 
with  the  sulphate  of  copper  increases  the  conductivity  of 
the  liquid. 

Endosmose  causes  the  liquid  in  the  porous  jar  to  rise 
slightly  above  that  in  the  outside  jar ;  finally,  evapora- 
tion causes  the  two  liquids  to  gradually  descend  and  in- 
creases the  richness  of  the  solution. 

All  these  reasons,  and  others  which  we  will  soon  give, 
go  to  prove  that  the  resistance  of  Daniell's  battery  is 
constantly  changing ;  every  time  it  is  measured  it  is 
found  to  be  different. 

The  intensity  of  the  current  of  Daniell's  battery,  as 
has  been  shown,  varies  considerably  from  one  day  or 
from  one  hour  to  another,  and  as  the  electro-motive  force 
does  not  change,  it  is  clear  that  it  must  be  the  resistance 
which  varies. 

Figures  relating  to  the  resistance  of  battery  cells  would 
possess  but  little  interest,  as  they  can  only  be  approxi- 
mate, and  applicable  only  to  jars  and  electrodes  of  deter- 
mined dimensions,  and  to  certain  heights  of  the  liquids 
in  the  jars. 

SELECTION  OF  CELLS. 

In  general,  larger  cells  are  used  for  local  circuits,  and 
smaller  ones  for  telegraph  lines,  because  the  former  are 


92  TWO-LIQUID    BATTERIES. 

less  resistant  than  the  latter ;  this  difference  results  from 
the  fact  that  the  immersed  surface  of  the  electrodes  is 
greater  in  the  large  ones,  whereas  their  distance  is  almost 
the  same. 

Jf  things  were  looked  at  from  a  physical  point  of  view 
only,  the  use  of  large  cells  would  always  be  advanta- 
geous ;  but  in  the  practice  there  are  other  things  to  be 
taken  into  consideration.  The  convenience,  and  above 
all  the  economy  in  buying  and  keeping  them  in  order, 
must  be  thought  of.  Large  cells  are  more  cumbersome 
and  more  exposed  to  accidents ;  besides,  they  are  especi- 
ally dear,  and  the  necessary  supply  of  sulphate  of  copper 
and  zinc  plates  tends  to  increase  the  expense. 

Conseqiiently  the  use  of  cells  as  small  as  possible  is 
recommended.  It  is  necessary  to  understand  perfectly 
how  in  long  circuits  resisting  batteries  present  but  few 
inconveniences,  and  how  the  larger  cells  are  preferable  in 
short  circuits. 

If  in  a  very  long  circuit,  of  3000  units  of  resistance, 
for  instance,  with  a  receiving  instrument  of  1000  units, 
a  battery  of  25  cells  of  10  units  each  be  employed,  the 
total  resistance  of  the  battery  will  be  250  units,  and  that 
of  the  whole  circuit  4250.  The  resistance  of  the  battery 
is  thus  but  a  small  fraction  of  that  of  the  whole  circuit ; 
consequently  the  substitution  of  smaller  cells,  even  if 
their  resistance  were  twice  as  great  as  that  of  the  first 
ones,  would  not  greatly  increase  the  resistance  of  the 
circuit,  nor,  consequently,  the  intensity  of  the  current. 
But  if,  on  the  other  hand,  we  take  a  short  circuit  of  2 
units  with  a  receiving  instrument  of  3  units,  and  use  a 
battery  of  5  cells,  each  having  10  units  of  resistance, 
there  will  be  in  the  battery  50  units  and  in  the  circuit  55 
units  of  resistance. 


DANIELL'S  BATTERY.  93 

It  is  seen  that  the  resistance  of  a  battery  is  the  most 
important  element,  and  by  diminishing  it  one  half  by  the 
substitution  of  larger  cells  the  resistance  of  the  circuit 
will  be  reduced  to  30  units,  and  consequently  the  inten- 
sity of  the  current  will  almost  be  doubled.  Let  us  follow  up 
this  idea.  The  intensity  of  the  current  being  much  greater 
with  the  5  new  cells  of  5  units  of  resistance  each,  their 
number  might  be  reduced  to  3,  for  instance ;  the  resist- 
ance of  the  battery  would  then  be  15,  that  of  the  circuit 
20,  and  finally  the  intensity  of  the  current  (^  or  £)  would 
be  still  greater  than  that  we  had  at  the  beginning.  Thus 
for  a  short  circuit  larger  cells  should  be  used,  only  less 
in  number,  by  which  a  saving  is  obtained. 

POROUS  JARS. — The  porous  partitions  which  separate 
the  liquids  in  constant  batteries  are  generally  made  of 
porous  porcelain ;  but  one  can  use  wood,  carbon,  blad- 
ders, canvas,  pipe-clay,  paper  pulp,  and  in  general  all 
substances  not  chemically  acted  upon  by  the  liquids. 

In  his  first  experiments  Daniell  used  a  piece  of  bladder 
inside  of  and  having  the  shape  of  a  copper  tube  pierced 
with  holes,  which  served  as  the  negative  electrode  of  his 
cell ;  this  membrane  partition  presented  great  advantages, 
its  cylindrical  form  was  excellent,  and  it  was  very  gener- 
ally adopted;  it  was  very  porous  and  electrically  but 
little  resistant.  It  was  abandoned  because  it  was  too 
porous  and  too  fragile. 

Finally  porous  jars,  properly  so  called,  were  brought 
into  use ;  they  are  made  of  porous  -porcelain.  We  will 
here  only  speak  of  this  latter ;  those  made  of  parchment 
paper,  canvas,  etc.,  will  be  treated  of  in  the  description 
of  those  batteries  in  which  they  are  used. 

We  have  explained  how,  in  the  regular  and  theoretical 
action  of  Daniell's  cell,  copper  is  deposited  upon  the  cop- 


94  TWO-LIQUID   BATTERIES. 

per  electrode.  In  the  practice  it  is  found  that  copper  is 
also  deposited  upon  the  inside  surface  of  the  porous  jar, 
and  even  in  the  pores,  which  are  finally  stopped  up  ;  after 
a  certain  time  the  jar  ceases  to  be  porous  enough  and 
should  be  replaced.  That  is  one  of  the  inconveniences 
of  this  form  of  Daniell's  cell,  which,  however,  should  not 
be  exaggerated,  as  the  porous  jars  are  very  cheap  and 
may  bo  replaced  at  very  little  expense. 

In  the  telegraph  service,  a  porous  jar  may  sometimes 
serve  six  months  or  a  year.  Purchasers  of  old  metals 
buy  these  porous  jars,  often  very  heavily  charged  with 
copper,  and  know  how  to  use  them  to  the  greatest  advan- 
tage. 

These  deposits  of  copper  in  the  interior  of  the  po- 
rous jar  frequently  present  a  very  interesting  peculiarity : 
they  show  themselves  upon  the  surfaces  with  a  tree-like 
aspect ;  it  is  a  slow  crystallization,  which  reminds  one  of 
the  unfolding  of  a  fern. 

It  frequently  happens  that  the  deposit  of  copper  accu- 
mulates upon  certain  points  of  the  inside  surface,  and 
presents  a  crystalline  structure,  properly  so  called.  Crys- 
tals are  sometimes  seen  to  attain  the  dimensions  of  -£%  or 
^  of  an  inch. 

These  deposits  in  the  pores  and  upon  the  surface  of 
the  porous  jar  may  easily  be  accounted  for.  They  are  the 
result  of  an  electro-chemical  action  analogous  to  that  shown 
in  a  previous  experiment  by  De  La  Rive  upon  ordinary 
commercial  zinc  compared  with  chemically  pure  zinc. 
The  porcelain  contains  various  heterogeneous  particles, 
which  produce  local  actions  and  also  the  decomposition  of 
the  sulphate  of  copper.  It  is  probable  that  this  deposit 
takes  place  very  slowly  at  first,  but  as  the  deposit  accu- 
mulates the  process  becomes  more  and  more  rapid. 


DANIELL'S  BATTEEY.  95 

These  deposits  of  copper  in  and  upon  the  walls  of  the 
porous  partition  possess  another  quality  which  we  should 
not  forget ;  namely,  that  of  diminishing  the  internal  re- 
sistance of  the  cell.  This  is  a  fact  that  oft-repeated  ex- 
periments have  proved.  The  explanation  seems  to  us 
very  clear.  The  porous  partition  presents  a  very  great 
electric  resistance,  because  the  total  section  of  the  canals 
filled  with  liquid  is  extremely  small.  When  a  portion  of 
this  section  is  replaced  by  copper,  a  metal  possessing 
great  conductivity,  the  resistance  should  be  reduced  in 
proportion. 

It  should  be  noted  that,  under  these  circumstances,  the 
copper  causes  no  polarization  of  the  electrodes,  otherwise 
the  results  would  be  entirely  different. 

All  this  would  lead  to  the  belief  that  the  choice  of 
porous  jars  had  great  influence  upon  the  intensity  of  the 
current,  by  changing  the  internal  resistance  of  the  cell. 
The  results  of  several  experiments  show,  however,  that 
jars  of  different  states  of  porosity  can  change  but  slightly 
the  resistance  of  cells. 

The  conclusion  points  to  the  preference  of  jars  of  little 
porosity  in  all  batteries  destined  for  continual  and  pro- 
longed work.  They  should  be  immersed  in  water  before 
charging  the  battery ;  or  better,  charge  the  battery  sev- 
eral hours  before  using  it,  in  order  to  allow  the  liquids  to 
penetrate  the  pores  and  come  into  contact  with  each 
other. 

Yery  porous  jars  have  the  disadvantage  of  allowing  the 
liquids  to  mix  too  easily ;  the  result  is  a  direct  action  of 
the  zinc  upon  the  sulphate  of  copper,  and  a  deposit  of  the 
copper  upon  the  zinc,  which  is  a  grave  fault  inherent  in 
Daniell's  battery,  and  upon  which  we  will  now  enlarge. 

LOCAL  ACTIONS  ;   WASTE. — The    sulphate   of    copper, 


96  TWO-LIQUID   BATTEKIES. 

which  penetrates  the  porous  partition,  comes  into  contact 
with  the  zinc,  and  is  decomposed  by  an  electro-chemical 
local  action.  Copper  is  deposited  upon  the  zinc  in  the 
shape  of  black  mud,  which  cannot  be  put  to  any  use. 
(This  black  powder  is  said  by  some  to  be  oxide  of  copper, 
but  this  is  an  error,  as  can  be  easily  shown  by  means  of 
some  feeble  acid,  as  acetic  acid.) 

This  action  does  not  co-operate  in  the  production  of 
the  current ;  it  takes  place  especially,  as  can  be  easily  un- 
derstood, with  very  porous  jars  ;  but  it  exists  in  every  ar- 
rangement of  DanielPs  cell,  as  will  be  seen  as  we  advanc •. . 

This  inconvenience  would  be  less  if  the  current  circu- 
lated continually ;  but  in  almost  all  applications,  batter- 
ies, and  especially  those  of  Daniell,  are  only  used  inter- 
mittently and  at  long  intervals.  Many  of  the  telegraph 
batteries  and  those  used  for  electric  bells  work  but  a  few 
minutes  daily,  thus  being  nearly  always  in  an  open  cir- 
cuit. Under  these  circumstances,  the  fault  of  which  we 
speak  is  at  its  maximum. 

It  is  understood  that  if,  on  the  contrary,  the  cells  are 
very  actively  employed,  as  in  an  important  telegraph 
office,  this  same  fault  is  less  grave ;  the  sulphate  of  cop- 
per and  the  zinc  are  consumed  much  more  usefully.  But 
even-  in  that  exceptional  case,  where  a  Daniell  cell  fur- 
nishes a  constant  current,  there  is  a  certain  quantity  of 
sulphate  of  copper  which,  penetrating  the  porous  jar,  is 
decomposed  by  its  contact  with  the  zinc,  and  deposits 
upon  the  latter,  copper  in  the  shape  of  black  mud. 

In  short,  we  can  say  that  an  ordinary  Daniell  cell  con- 
sumes almost  as  much  zinc  and  sulphate  of  copper  when 
its  circuit  is  open,  and  when  it  does  no  useful  work,  as 
when  its  circuit  is  closed,  and  when  it  really  acts  as  a  pro- 
ducer of  electricity. 


97 

This  is  about  the  only  fault  that  can  be  found  in  the 
Daniell  battery.  Its  gravity,  however,  has  often  led  to 
the  preference,  in  many  instances,  of  other  batteries,  such 
as  that  of  Leclanche,  which,  however,  do  not  fully  fill  the 
conditions  of  a  constant  battery. 

This  fault  is  present  in  the  Daniell  battery  to  a  greater 
or  less  degree,  according  to  the  porosity  of  the  jars. 
Among  the  improvements  upon  DanielFs  battery,  which 
we  will  soon  describe,  there  are  some  which  possess  the 
advantage  of  greatly  reducing  the  detrimental  effect  in 
question. 

The  copper,  by  entering  the  pores,  diminishes  the  po- 
rosity, thereby  improving  the  battery,  for  a  certain  length 
of  time  at  least.  But  it  is  plain  that,  if  the  porosity  be 
too  much  reduced,  the  battery  will  no  longer  work,  for  if 
the  pores  of  the  partition  are  completely  stopped  up,  it 
would  no  longer  furnish  any  current. 

Finally,  the  pure  loss  in  the  consumption  of  sulphate 
of  copper  is  less  when  the  solution  of  sulphate  is  less  con- 
centrated ;  and,  as  the  reduction  of  concentration  does 
not  diminish  the  electro-motive  force,  and  does  not  nota- 
bly increase  the  resistance,  there  is  a  great  advantage,  as 
can  be  seen,  in  not  using  a  saturated  solution  of  sulphate 
of  copper. 

It  should  be  noticed  that  the  deposit  of  copper  upon 
the  zinc  does  not  change  the  electro-motive  force  of  the 
cell,  which  confirms  what  we  said  of  the  constancy  of  this 
force  in  DanielFs  cell.  In  some  models,  the  zinc  is  sus- 
pended, so  that  it  may  not  rest  on  the  bottom  of  the  jar 
and  come  in  contact  with  any  rubbish  that  might  happen 
to  accumulate  there,  which  would  result  in  local  actions. 
It  is  an  established  fact  that,  in  ordinary  batteries,  the 
lower  part  of  the  zinc  is  more  consumed  than  that  near 


98  TWO-LIQUID   BATTERIES. 

the  top.  The  cause  of  this  is  due  partly  to  the  contact 
of  this  rubbish  with  the  zinc,  producing  local  actions. 

CLIMBING  SALTS. — The  Daniell  battery  possesses  one 
more  little  fault  that  should  not  be  left  unnoticed. 
When  the  liquid  in  the  outside  jar  begins  to  become  sat- 
urated with  sulphate  of  zinc,  climbing  salts  are  formed, 
which  ascend  the  walls  of  the  outside  jar,  and  even  of  the 
porous  jar,  running  over  the  rim  of  the  former  and  de- 
scending on  the  outside.  All  this  can,  however,  be  avoid- 
ed by  proper  care  and  attention.  These  salts  establish 
permanent  communication  between  the  different  elements 
of  the  cell,  which  communication  contributes  to  the 
waste.  The  manner  in  which  these  salts  are  formed  is 
very  easy  to  understand. 

In  the  beginning,  either  by  a  slight  movement  or  other- 
wise, some  of  the  liquid  is  thrown  upon  the  sides  of  the 
jar.  Evaporation  causes  the  disappearance  of  the  water 
and  leaves  crystals.  Immediately,  capillary  action  sets  in, 
either  between  the  crystals  and  the  side  of  the  jar,  or  along 
the  side  of  the  crystals,  and  a  small  quantity  of  liquid  thus 
rises  above  the  general  level. 

Evaporation  again  causes  the  formation  of  new  crystals, 
which  is  facilitated  by  the  thinness  of  the  layer.  This 
action  continues  step  by  step  horizontally  and  vertically. 

As  long  as  the  formation  of  climbing  salts  does  not  run 
over  the  top  of  the  glass  jar,  or  establish  any  permanent 
communication  between  the  elements,  it  is  not  unfavora- 
ble. It  might  indeed  be  considered  as  an  advantage,  as  it 
reduces  the  concentration  of  the  sulphate  of  zinc  solution. 
"We  have  previously  shown  by  figures  that  a  saturated 
solution  has  less  conductivity  than  when  diluted  to  half. 
When  the  solution  is  saturated,  it  is  incapable  of  dissolv- 
ing the  salt  formed  by  the  action  of  the  battery,  and  the 


99 

most  unfavorable  thing  that  can  then  happen  is  a  deposit 
of  crystallized  sulphate  of  zinc  upon  the  zinc  or  upon  the 
immersed  part  of  "the  porous  jar,  for  it  stops  the  chemical 
action  or  the  communication  of  the  liquids.  It  is  there- 
fore advisable  to  take  the  climbing  salts  completely  away 
and  not  to  put  them  back  in  the  glass  jar. 

To  suppress  the  production  of  climbing  salts,  it  has 
been  proposed  to  spread  a  thin  layer  of  oil  upon  the  sur- 
face of  the  liquids,  which  would  check  all  evaporation ; 
this  has,  however,  received  no  application,  on  account  of 
the  uncleanliness  it  would  inevitably  cause.  This  layer 
of  oil  would  also  occasion  rapid  concentration,  which,  as 
we  have  stated,  diminishes  the  conductivity.  The  climb- 
ing salts  may  be  kept  from  running  over  the  top  of  the 
glass  jar  by  smearing  the  top  with  some  greasy  substance 
(paraffin,  for  instance). 

Climbing  salts  of  sulphate  of  zinc  are  very  easily  de- 
tached from  the  glass,  either  with  the  fingers  or  with  a 
rag ;  but  they  hold  much  more  firmly  to  the  porous  jar, 
and  it  is  with  difficulty  that  they  may  be  detached  from 
it  by  rubbing.  Therefore,  the  top  part  of  the  porous  jar 
which  stands  out  of  the  liquid  should  be  carefully  glazed ; 
the  salts  may  then  be  taken  off  as  easily  as  from  the 
glass. 

IMPROVED  DANIELL  CELL. 

We  have  sought  to  construct  as  satisfactory  a  Daniell 
element  as  possible.  The  following  is  the  disposition 
that  we  have  decided  upon : 

The  positive  electrode  is  formed  of  a  cylinder  of  zinc 
surrounding  the  porous  jar,  and  is  held  at  a  small  distance 
from  the  latter  by  means  of  small  sticks  of  wood  placed 
vertically  between  the  two ;  the  zinc  and  the  small  sticks 


100  TWO-LIQUID   BATTERIES. 

are  held  in  their  place  by  being  tightly  bound  together  at 
the  top  and  bottom  with  pieces  of  string. 

The  connecting  strap  of  the  zinc  is  cut  out  of  the  same 
sheet  of  metal  as  the  cylinder  itself,  which  dispenses  with 
any  loss  in  the  cutting,  provided  two  cylinders  with  their 
connecting  straps  be  cut  out  of  the  same  piece,  one  in  the 
reverse  manner  from  the  other. 

The  copper  electrode  is  cut  in  the  same  manner  out  of  a 
sheet  in  the  form  of  a  cylinder,  which  is  placed  inside  the 
porous  jar ;  small  sticks  of  wood  placed  around  the  copper 
and  bound  to  it  with  string  keep  it  from  coming  into 
contact  with  the  interior  surface  of  the  porous  jar. 
'  At  two  thirds  of  the  height  of  the  copper  is  fixed,  with- 
out solderings  and  simply  fastened  in  the  copper,  a  circular 
piece  of  copper  pierced  with  holes,  thus  forming  a  parti- 
tion without  impeding  the  movement  of  the  liquid. 
Upon  this  partition  are  placed  sulphate  of  copper  crystals, 
which  hold  the  solution  at  saturation. 

In  the  outer  jar  is  put  a  solution  of  sulphate  of  zinc 
possessing  its  maximum  conductibility ;  that  is,  a  solution 
at  first  saturated  and  then  diluted  with  its  bulk  of  water 
(specific  weight  about  1.10).  This  disposition  is  intended 
to  reduce  to  a  minimum  the  internal  resistance  of  the  ele- 
ment, and  to  render  it  as  compact  and  solid  as  possible. 
For  experiments  of  precision  it  is  best  to  ascertain,  at 
first  starting,  the  density  of  the  sulphate  of  zinc  by  means 
of  an  hydrometer,  and  to  always  keep  it  the  same  by  add- 
ing, from  time  to  time,  some  pure  water,  as  the  solution 
becomes  concentrated  either  by  evaporation  or  by  the 
formation  of  sulphate  of  zinc  in  the  battery. 

Undoubtedly  the  use  of  a  saturated  solution  of  sul- 
phate of  copper  greatly  increases  the  expense  of  the  bat- 
tery, but  we  are  now  supposed  to  be  talking  of  an  appara- 


DANIELL'S  BATTERY.  101 

tus  designed  for  experiments  of  precision  and  in  which  the 
question  of  expense  is  secondary.  ,  .  \y 

From  this  point  of  view  the  precautions  that  we  Jiave 
suggested  appear  to  us  to  be  indispensable  How  jri^ea' 
could  the  internal  resistance  of  a  cell  be  advantageously 
measured  unless  the  respective  distances  between  the  elec- 
trodes were  invariable  and  the  composition  of  the  liquids 
known  and  determined  ? 

It  is  only  with  elements  arranged  in  the  above  manner 
that  it  may  be  hoped  to  obtain  concordant  or  even  com- 
parable results.  In  truth,  it  is  very  probable  that  these 
precautions  will  not  be  sufficient,  but  they  are  necessary. 

BALLOON  BATTEEY. 

Another  arrangement  of  DanielFs  battery,  represented 
by  Fig.  22,  has  been  and  is  still  used  in  some  countries. 
It  needs  no  attention  for  six  months,  or  more,  at  a  time. 
The  flask,  which  surmounts  the  cell,  contains  two  pounds 
of  sulphate  of  copper  crystals,  and  is  filled  with  water. 
The  flask  is  closed  with  a  perforated  cork  fitted  with  a 
glass  tube ;  this  tube  descends  as  far  as  the  liquid  in  the 
porous  jar.  The  solution  of  sulphate  of  copper  being 
more  dense  in  proportion  as  it  is  more  concentrated,  it  can 
be  seen  that  the  part  of  this  solution  which  is  in  the  po- 
rous jar  is  constantly  held  at  saturation,  for  as  it  weakens 
it  is  supplied  by  the  saturated  solution  which  descends 
from  the  flask. 

The  glass  jar  of  the  cell  is  closed  with  a  wooden  lid, 
which  supports  the  flask.  The  result  is  that  evaporation 
is  reduced  to  almost  nothing,  and,  consequently,  there  is 
a  very  slight  or  no  formation  at  all  of  climbing  salts,  and 
the  liquid  is  preserved. 


102 


TWO-LIQUID   BATTERIES. 


This  battery  lias  been  known  to  work  for  more  than  a 
ye'ar  without'  ?eqmring  any  attention,  during  which  time 
it  .satisf aeterily  met'  all  practical  requirements. 


It  has,  however,  been  replaced  by  more  economical 
batteries,  such  as  Callaud's  or  Leclanche's. 


A  EEYERSED  FOBM  OF  DANTELL'S  BATTEEY. 

For  a  long  time  Daniell's  battery  was  arranged  in  a 
manner  the  reverse  of  that  which  we  have  already  de- 
scribed. The  zinc,  in  the  shape  of  a  solid  cylinder, 
which  served  as  soluble  electrode,  was  placed  inside  of 
the  porous  jar,  instead  of  outside.  The  copper  was  placed 
around  the  outside  of  the  porous  jar,  serving  at  the  same 
time  as  conducting  electrode  and  as  the  jar  containing 


DANIELL'S  BATTERY.  103 

the  liquid.  In  addition  to  the  exterior  hollow  copper 
cylinder,  another  was  placed  nearer  the  porous  jar,  in  or- 
der to  diminish  the  resistance  of  the  cell.  This  interior 
cylinder  of  copper  was  pierced  with  holes,  to  facilitate 
the  circulation  of  the  liquid  (solution  of  copper  sulphate). 
Finally,  crystals  of  copper  sulphate  were  put  between 
the  two  copper  cylinders,  in  order  to  keep  the  solution  in 
a  state  of  saturation,  in  spite  of  the  consumption  of  the 
battery. 

At  first  sight,  this  arrangement  would  appear  to  be 
much  superior  to  that  previously  described.  In  this  one 
the  glass  jar  is  suppressed,  and  -consequently  the  many 
accidents  resulting  from  its  brittleness  are  avoided.  It 
has,  however,  been  abandoned  for  the  first  arrangement 
on  account  of  the  following  reasons  : 

1st.  The  battery  with  the  copper  jar  costs  a  great  deal 
more,  because  of  the  large  quantity  of  copper  required, 
and  also  on  account  of  the  quantity  of  copper  sulphate 
with  which  the  battery  is  charged  at  the  beginning. 

2d.  The  copper  jar  might  become  pierced,  and  the 
liquid  would  then  leak  out ;  a  few  impurities  in  the  metal 
would  suffice  to  set  up  local  electro-chemical  actions,  and 
thus  bring  about  perforation. 

3d.  Cast  zinc  is  used,  which  presents  another  disadvan- 
tage. For,  during  the  process  of  casting,  very  often  little 
cavities  are  formed  in  the  zinc,  into  which  the  liquid  pene- 
trates, thereby  producing  local  actions  and  uselessly  con- 
suming the  zinc. 

4th.  The  zinc  nearly  fills  the  porous  jar,  thus  leaving 
but  little  room  for  the  liquid,  which  is  soon  saturated 
with  the  sulphate  of  zinc  and  becomes  incapable  of  dis- 
solving any  more.  This  is  a  grave  fault  in  the  working 
of  the  battery. 


104  TWO-LIQUID   BATTERIES. 

"We  must  do  Daniell  the  justice  to  say  that  he  had 
foreseen  this  difficulty,  and  had  proposed  an  accessory 
arrangement  for  the  renewal  of  the  water  destined  to 
dissolve  the  sulphate  of  zinc ;  but  this  addition  compli- 
cated the  apparatus  and  increased  the  cost. 

The  cell  might  be  sensibly  improved  by  the  substitu- 
tion of  a  thin,  hollow  cylinder  of  zinc  for  the  massive 
zinc  used  above  ;  the  quantity  of  water  in  which"  the  zinc 
is  immersed  would  thus  be  greatly  increased. 

It  is  well  to  note,  before  leaving  this  subject,  that  the 
surface  of  the  negative  electrode  is  comparatively  much 
larger  than  that  of  the  soluble  electrode.  We  said,  in 
speaking  of  Wollaston's  battery,  that  this  condition  was 
very  favorable  in  single-liquid  batteries,  but  it  is  not  so 
in  two-liquid  batteries,  or  at  least  not  in  Daniell's  battery. 
Since  the  depolarization  of  the  negative  electrode  is  com- 
plete, there  is  no  advantage  in  increasing  its  surface. 
The  considerations  which  prevail  in  the  choice  of  elec- 
trodes have  been  clearly  indicated  in  that  which  we  have 
just  said. 

TKOUGH  BATTEKY. 

Still  another  arrangement  of  Daniell's  battery  is  rep- 
resented by  Fig.  23,  and  the  above  name  given  to  it. 

A  trough  is  made  of  teak  and  divided  into  ten  cells  by 
slate  partitions ;  each  cell  is  then  subdivided  by  a  porous 
partition  of  unglazed  porcelain.  A  zinc  plate  is  placed 
in  one  of  these  divisions,  and  a  thin  copper  plate  in  the 
next  one,  and  so  on,  until  the  ten  cells  are  occupied. 
The  copper  plate  of  one  cell  is  permanently  connected 
with  the  zinc  of  the  next  cell  by  a  copper  strap  cast  into 
the  zinc  and  riveted  to  the  copper,  which  is  easily  bent 
over  the  slate  partition. 


DANIELL'S  BATTERY. 


105 


The  last  copper  and  the  last  zinc  plate  are  each  con- 
nected to  brass  binding  screws  or  terminals,  which  be- 
come respectively  the  positive  and  negative  poles  of  the 
battery. 

A  solution  of  sulphate  of  copper  and  a  few  crystals  are 
placed  in  the  copper  divisions ;  in  the  others,  pure  water 
or  a  very  weak  solution  of  sulphate  of  zinc. 

This  arrangement  presents  great  advantages;  it  dis- 
penses with  glass  jars,  which  sometimes  break  without 
any  apparent  cause.  The  trough  is  made  water-tight  by 
coating  it  internally  with  marine  glue,  and  the  liquids 
ought  not  to  leak  out.  But  it  unfortunately  happens, 
sometimes,  that  the  marine  glue  chips  off,  and  one  cell 


FIG.  23. 

becomes  leaky.     When  this  occurs,  the  battery  must  be 
repaired. 

The  trough  is  very  solid,  and  is  easily  transported  when 
not  charged  with  liquid.  The  zinc  and  copper  electrodes 
of  each  cell  are  at  a  well-regulated  distance  from  each 
other,  and  do  not  touch  the  porous  partition  if  the  bat- 
tery is  carefully  charged. 


106 


TWO-LIQUID   BATTEEIES. 


These  last  conditions  are  fulfilled  with  difficulty  where 
cylindrical  elements  are  used.  The  trough  having  a 
wooden  lid,  there  is  very  little  evaporation.  Of  all  known 
forms,  this  is  the  least  cumbersome. 

The  dimensions  of  the  electrodes  are  generally,  for  the 
zinc,  3£  in.  by  2  in.,  and  for  the  copper,  3  in.  square. 
The  battery  will  work  a  month  without  the  necessity  of 
opening  the  trough.  One  of  these  batteries  of  ten  cells 
costs  $5.25,  and  the  keeping  it  in  order  $2  per  annum. 


CONVENTIONAL  FIGURE. 

Batteries  are  generally  represented  by  a  conventional 
figure,  which  originally  represented  Daniell's  trough  bat- 


•HttH- 


FIG.  24 


tery,  or  the  sand  battery,  of  which  we  epoke  in  Part  L 
Each  cell  is  represented  by  two  lines  (Fig.  24),  the  short 
and  thick  one  representing  the  zinc,  and  the  long  and 
narrow  one  the  copper.  Z  and  C  mark  respectively  th? 
negative  and  positive  poles  of  the  battery. 


DANIELL'S  BATTEEY. 


107 


MUIRHEAD'S  BATTERY. 

There  are  a  great  many  such  in  use  in  England 

The  outside  jar  is  made  of  white  porcelain  and  is 


square.     The  porous  jar,  made  of  red  earthenware,  coir 
tains  the  negative  electrode  and  the  sulphate  of  copper, 


108  TWO-LIQUID   BATTEKIES. 

and  is  placed  in  the  square  porcelain  jar,  which  contains 
the  zinc  electrode  and  the  sulphate  of  zinc.  The  elec- 
trodes are  the  same  as  in  the  preceding  battery. 

For  economical  reasons  these  cells  are  taken  by  twos ; 
that  is,  each  outside  porcelain  jar  contains  two  compart- 
ments and  two  complete  cells.  This  arrangement  pre- 
sents a  very  favorable  condition,  which  is  also  met  with 
ill  the  cylindrical  cells  described  at  the  beginning ;  viz., 
the  compartment  containing  the  sulphate  of  zinc  is  quite 
large.  Fig.  25  represents  several  of  these  cells  together. 

CAEEfi'S  BATTEEY. 

Carre's  battery  differs  from  the  ordinary  Daniell  bat- 
tery simply  in  the  substitution  of  a  vessel  made  of 
parchment  paper  for  the  ordinary  porous  jar.  This 
porous  partition  offered  very  little  resistance,  which  re- 
alized the  object  of  its  inventor.  The  whole  battery 
indeed  was  arranged  with  a  view  to  diminishing  the  re- 
sistance. The  zinc  cylinders  were  22  in.  high  and  4-J  in. 
in  diameter. 

Sixty  of  these  cells  were  used  by  M.  Carre  for  electric- 
light  purposes,  which  is,  wre  think,  worthy  of  mention, 
as  it  was  the  first  time  that  DanielPs  battery  had  been  tried 
in  that  way. 

In  fact,  M.  Carre's  arrangement  was  only  fit  for  elec- 
tric-light purposes ;  that  is,  to  furnish  a  continuous  cur- 
rent of  great  intensity  for  several  hours.  The  frailty  of 
the  porous  partition  rendered  the  battery  useless  for  any 
work  of  long  duration.  We  believe,  however,  that  this 
battery,  in  spite  of  the  disadvantage  we  have  pointed 
out,  should  again  be  taken  up  by  persons  interested  in 
the  electric  light,  who  could  give  it  a  fixed  place  and 


DANIELL'S  BATTERY.  109 

could  take  care  of  it.  In  the  use  of  this  battery,  the  dis- 
agreeable acid  vapors,  which  are  dangerous  to  inhale, 
would  be  avoided,  and  the  expense  would  be  compara- 
tively small. 

This  battery  has  been  known  to  work  200  successive 
hours  without  any  sensible  weakening,  by  carefully  re- 
placing, every  2i  hours,  a  part  of  the  sulphate  of  zinc 
with  pure  water. 

SIEMENS  AND  HALSKE'S  BATTERY. 

This  battery  is  a  Daniell  battery  with  a  porous  jar, 
like  those  which  precede,  and  is  very  extensively  em- 
ployed in  Europe. 

The  copper,  <?,  is  at  the  bottom  of  the  glass  jar  (Fig.  26), 
and  the  diaphragm  or  porous  jar  has  the  form  of  a  bell. 
A  thing  to  be  noted  is  the  central  chimney,  in  which 
there  is  a  glass  tube  through  which  a  copper  wire,  at- 
tached to  the  negative  electrode,  passes,  forming  the  con- 
nection of  the  positive  pole.  The  porous  jar  sustains  a 
mass  of  paper  pulp,  dampened  with  sulphuric  acid,  and 
then  dried.  The  zinc,  2,  placed  on  top  of  the  pulp,  is  a 
very  thick  cylinder,  melted  in  a  mould  and  carrying  a 
vertical  appendix,  to  which  the  positive  connection  of 
the  adjoining  cell  is  attached. 

The  arrangement  of  this  battery  has  been  changed 
several  times.  At  first  there  was  no  porcelain  porous 
jar,  but  simply  the  paper  pulp.  The  general  character- 
istics, however,  have  remained  the  same.  The  great 
thickness  of  the  porous  jar  suppresses  almost  completely 
the  diffusion  of  the  sulphate  of  copper,  and  consequently 
the  waste  chemical  action  and  the  useless  consumption  of 
zinc  and  sulphate  of  copper  are  avoided.  On  the  other 


110 


TWO-LIQUID   BATTERIES. 


hand,  however,  the  internal  resistance  of  the  cells  is  con- 
siderable, so  that  they  cannot  be  used  as  local  batteries. 


FIG.  26. 

YAELEY'S  BATTERY. 

Cromwell  Varley  suggested  a  means  of  completely  sup- 
pressing the  passing  of  the  sulphate  of  copper  through 


DANIELL'S  BATTERY.  Ill 

the  porous  partition,  a  thing  which  Siemens  and  Halske 
only  slightly  diminished  and  slackened.  This  means  con- 
sists in  the  substitution  of  oxide  of  zinc  for  the  paper 
pulp  in  the  preceding  battery.  It  is  easily  understood 
that  the  sulphate  of  copper,  which  enters  the  mass  of 
oxide  of  zinc,  forms  sulphate  of  zinc,  and  deposits  oxide 
of  copper  in  the  shape  of  a  black  powder. 

This  original  idea  was  perhaps  never  put  into  applica- 
tion outside  of  Varley's  laboratory.  But  it  deserves 
notice,  for  it  shows  the  reader  what  an  infinite  variety 
of  resources  chemistry  presents  to  those  who  know  how 
to  search  for  them. 

It  is  clear  that  this  porous  partition  becomes  destroyed 
in  time ;  it  is  also  very  resistant.  These  are  all  incon- 
veniences in  daily  practice,  but  are  unimportant  in  labo- 
ratory experiments,  which  require  as  perfect  a  battery  as 
possible. 

MHSTOTTO'S  BATTEKY. 

This  is  in  form  a  Daniell  battery,  extensively  used  in 
Italy  and  throughout  British  India.  It  consists  of  a  jar, 
at  the  bottom  of  which  is  a  copper  plate  fitted  with  a 
wire  covered  with  gutta-percha,  which  ascends  to  the 
top  of  the  jar  and  serves  as  a  connection.  This  electrode 
is  covered  with  an  inch  of  crushed  sulphate  of  copper, 
this  again  with  a  layer  of  river  sand,  and  finally  a  plate 
of  zinc  of  considerable  thickness.  The  crushed  sulphate 
of  copper  is  separated  from  the  sand  by  a  piece  of 
cloth  or  blotting-paper.  Sir  William  Thomson  recom- 
mends sawdust  instead  of  sand.  The  zinc  is  of  con- 
vex form,  in  order  to  permit  the  freeing  of  bubbles  of 
hydrogen  which  sometimes  form  themselves  in  Daniell's 
battery. 


112 


TWO-LIQUID   BATTEEIES. 


These  batteries  last  eighteen  or  twenty  months  upon 
important  telegraph  lines,  and  as  long  as  thirty-two 
months  upon  less  important  lines. 


TROUYE'S  BLOTTING-PAPER  BATTERY. 

Trouve's  battery  is  one  of  the  latest  modifications  of 
Daniell's  battery.     Pig.  27  represents  a  separate  cell. 


FIG.  27. 

At  the  top  there  is  a  plate  of  zinc,  at  the  bottom  a 
plate  of  copper,  and  between  the  two  a  considerable 
thickness  of  blotting-paper.  The  upper  half  of  the  blot- 
ting-paper is  wet  down  with  a  concentrated  solution  of 
sulphate  of  zinc,  and  the  lower  half  with  sulphate  of 
copper.  We  have,  therefore,  all  the  elements  of  a  Daniell 
battery. 

It  is  of  course  plainly  understood  that  when  this  bat- 
tery is  perfectly  dry  it  is  absolutely  inert.  To  make  a 
source  of  electricity,  or,  more  simply,  a  voltaic  cell,  water 
must  be  added ;  only  that  quantity  which  the  paper  can 
absorb  is  necessary.  Thus  there  is  no  free  liquid,  and 
Trouve  might  have  called  his  battery  a  moist  lattery,  in 


DANIELL'S  BATTERY.  113 

order  to  distinguish  it  from  liquid  batteries  properly  so 
called. 

Let  us  return  to  the  description  of  the  cell.  The  two 
electrodes  and  the  blotting-paper  are  held  by  a  central 
piece  of  copper,  insulated  by  a  tube  of  ebonite,  which 
goes  above  the  zinc  and  penetrates  the  cover  of  the  glass 
jar,  whose  edges  should  be  well  ground  in  order  to  pre- 
vent all  evaporation.  This  central  piece  of  copper  is 
finally  furnished  with  a  binding  screw,  to  which  the  con- 
nection of  the  adjoining  cell  or  of  the  circuit  is  fastened ; 
the  negative  pole  is  a  copper  wire  soldered  to  the  upper 
part  of  the  zinc  electrode. 

Several  advantages  of  this  battery  are  easily  seen. 
When  it  is  dry  there  is  no  waste  whatever,  although  it  be 
charged.  To  dry  it,  it  is  only  necessary  to  expose  it  for 
a  few  hours  to  the  sun  or  to  a  current  of  air.  If  it  is  to 
be  used,  the  elements  must  only  be  moistened.  If  the 
cells  are  separated  from  each  other  like  the  one  repre- 
sented in  the  figure,  they  must  be  put  under  the  faucet  of 
a  fountain  which  runs  slowly.  This  operation  should  be 
repeated  after  a  short  interval,  in  order  to  allow  the  first 
water  to  saturate  the  paper  to  the  centre.  The  cell  is 
sufficiently  moist  when,  by  pressing  the  zinc  and  the 
copper  between  the  thumb  and  index,  drops  of  water  are 
seen  to  ooze  out  upon  the  surface  of  the  paper.  When 
several  cells  are  attached  to  the  same  cover,  as  in  the 
military  or  medical  batteries  which  we  will  describe  far- 
ther on,  they  are  immersed  in  special  vessels  and  left 
there  about  a  half-minute.  Whatever  the  method  be 
(and  the  choice  is  not  of  much  importance)  of  moist- 
ening the  elements,  this  done,  they  are  placed  in  the 
glass  jar  or  in  the  ebonite  box,  where  they  may  re- 
main several  months,  always  ready  for  work,  and  indeed 


114  TWO-LIQUID   BATTERIES. 

continually  working  and  furnishing  a  remarkably  regular 
current. 

This  regularity  constitutes  a  new  advantage  in  Trouve's 
battery,  upon  which  we  will  insist  before  passing  to  its 
applications. 

The  liquids  of  ordinary  batteries  have  a  movement  but 
slightly  impeded  by  the  porous  jar,  which  results  in  their 
mingling,  as  we  have  several  times  explained.  The  con- 
sequence is  that  local  actions,  which  disturb  the  normal 
working  of  the  battery,  take  place  and  occasion  waste. 

In  Trouve's  arrangement  the  movement  of  the  liquid 
is  almost  suppressed,  consequently  there  is  very  little 
mixing  of  the  sulphate  of  copper  with  the  sulphate  of 
zinc,  and  there  are  scarcely  any  local  actions ;  that  is,  there 
is  no  reduction  of  the  sulphate  of  copper  upon  the  sur- 
face of  the  zinc.  An  evident  economy  of  matter  con- 
sumed by  the  battery,  and  other  interesting  facts,  are  the 
results.  The  liquids  keep  their  respective  positions  al- 
most without  mixing,  the  resistance  varies  very  slowly, 
and  consequently  the  intensity  of  the  current  possesses 
great  constancy. 

We  have  often  made  the  following  experiment  with  a 
Daniell  porous-jar  battery.  Having  closed  the  circuit  in 
the  evening  upon  a  galvanometer,  it  was  found  in  the 
morning,  twelve  hours  later,  that  the  deflection  was  ex- 
actly the  same.  But  if  the  circuit  were  opened  only  one 
minute  and  then  again  closed,  there  was  observed  a  nota- 
ble difference. 

If  the  same  experiment  be  made  with  Trouve's  bat- 
tery, the  intensity  of  the  current  is  found  to  be  the  same, 
after  the  momentary  rupture  of  the  circuit,  as  it  was  be- 
fore. 

This  difference  in  the  results  shows  that  the  variation 


DANIELL'S  BATTEEY.  115 

of  the  resistance  takes  place  suddenly  and  abruptly  in  the 
ordinary  Daniell  cell,  and  on  the  other  hand  very  slowly 
in  Trouve's  arrangement. 

We  have  insisted  upon  the  constancy  of  the  electromo- 
tive force  of  Daniell's  battery  in  general.  Under  the 
form  given  to  it  by  Trouve  is  added  that  very  important 
quality  which  consists  in  the  existence  of  a  slightly  varia- 
ble resistance. 

RECHARGE  OF  THE  CELL. — When  the  cell  has  worked 
several  months,  more  or  less,  the  sulphate  of  copper  is 
used  up  and  converted  into  sulphate  of  zinc,  and  in  order 
to  give  to  the  cell  its  first  energy  it  must  be  recharged  in 
the  following  manner : 

The  sulphate  of  zinc,  which  has  taken  the  place  of  the 
sulphate  of  copper  in  the  lower  half  of  the  paper,  must 
be  dissolved  in  pure  water.  For  this  purpose  there  are 
especial  vessels  having  the  desired  level  of  the  water 
marked  upon  their  sides,  for  the  sulphate  of  zinc  which 
is  in  the  upper  half  must  not  be  dissolved.  This  same 
vessel  must  then  be  filled  to  the  same  level  with  a  warm 
saturated  solution  of  sulphate  of  copper,  in  which  the 
lower  half  of  the  elements  are  immersed  and  left  there 
three  or  four  minutes.  At  the  end  of  this  time  the  sul- 
phate will  have  penetrated  from  the  circumference  to  the 
centre  of  the  paper,  and  the  cell  is  recharged.  The  cell 
should  then  be  left  to  dry,  and  when  it  is  to  be  used 
it  should  be  dampened  as  we  have  said  in  the  begin- 
ning. 

MILITARY  BATTERY. — Trouve's  battery  has  been  ap- 
plied in  military  telegraphing  and  with  very  good  results. 
This  battery  consists  of  nine  cells,  distributed  in  three 
boxes,  each  containing  three  cells,  as  shown  in  Fig.  28. 
The  boxes  are  made  of  ebonite,  and  have  slate  lids,  to 


116  TWO-LIQUID   BATTERIES. 

which  the  cells  are  attached  as  in  the  separate  cell,  Fig. 
27.  The  three  boxes  are  then  placed  one  above  another 
in  the  desired  order,  and  enclosed  in  a  large  oaken  box. 
This  outside  box  is  carried  by  means  of  a  strap  thrown 


FIG.  28. 

over  the  shoulder,  or  placed  upon  a  wooden  frame  fas- 
tened on  the  back.  The  cells  are  2J-  in.  in  diameter 
and  1^-  in.  in  thickness. 

MEDICAL  BATTERY. — For  the  medical  application  of  a 
continuous  current,  Trouve  arranged  a  battery  of  three 
small  cells,  each  being  about  an  inch  in  diameter  and  1-J 
in.  in  thickness.  The  result  shows  a  considerable  re- 
sistance. These  cells  are  taken  by  forties,  sixties,  or 
eighties,  and  attached  to  a  single  piece  of  slate,  and  placed 
in  a  water-tight  wooden  box,  to  the  cover  of  which  the 
connections  are  fastened,  so  that  the  whole  or  only  part 
of  the  battery  may  be  used  at  will. 

These  cells  last  a  long  time,  because  they  contain  a 


DANIEL!/ 8   BATTERY.  117 

comparatively  great  quantity  of  sulphate  of  copper,  and 
because  they  work  in  circuits  of  very  great  resistance. 

There  is  a  very  decided  advantage  in  their  great  in- 
ternal resistance  for  medical  purposes ;  for  the  quantity 
of  electricity  which  circulates  is  very  small,  and  the 
electro-chemical  decomposition  at  the  contact  of  the  con- 
ductors with  the  body  of  the  patient  is  insensible. 

EESISTANCE  IN  TROUVE'S  BATTERY.— The  largest  model 
yet  made  is  3^  in.  in  diameter  and  2|-  in.  in  thick- 
ness. It  is  understood  that,  with  this  thickness,  the  re- 
sistance of  the  cell  is  inversely  proportional  to  the  sec- 
tion of  the  disc  electrodes.  The  regular  form  of  these 
cells  is  much  more  convenient  than  that  of  ordinary 
liquid  batteries  for  exact  calculations. 

By  modifying  the  diameter  of  the  electrodes  and  the 
thickness  of  the  blotting-paper  between  them,  the  resist- 
ance may  be  regulated  at  will. 


CHAPTER  II. 
GRAVITY    BATTERIES. 

SEVERAL  physicists  became  possessed,  at  the  same  time, 
of  the  idea  of  suppressing  the  porous  jar,  and  of  separat- 
ing the  liquids  by  their  difference  in  density.  Notable 
among  these  physicists  were  Callaud,  Meidinger,  and 
Yarley.  The  last  mentioned  took  out  a  patent  before 
any  of  his  competitors,  in  1855. 

CALLAUD'S  BATTERY. — This  battery  has  been  greatly 
improved  since  its  first  appearance.  The  following  are 
the  dimensions  of  the  one  most  in  use : 

From  the  top  of  a  glass  jar  8  in.  high  is  suspended  a 


FIG.  29. 


cylinder  of  zinc  2  in.  high.  It  is  held  by  three  hooks 
riveted  in  the  zinc  and  resting  on  the  rim  of  the  jar. 
The  copper  electrode  is  formed  of  a  thin  strip  of  copper 


GRAVITY   BATTERIES.  119 

rolled  in  the  shape  of  a  cylinder  !£-  in.  high  and  1J  in. 
in  diameter,  and  is  placed  at  the  bottom  of  the  jar.  A 
copper  wire  covered  with  gutta-percha  and  riveted  to 
the  copper  cylinder  passes  through  the  liquid,  and  being 
twice  bent,  is  soldered  to  the  zinc  of  the  adjoining  cell. 
If  the  wire  were  not  insulated  by  the  gutta-percha,  it 
would  be  liable  to  be  cut  at  the  line  of  separation  of  the 
two  liquids.* 

The  solution  of  sulphate  of  copper  is  at  the  bottom  of 
the  jar,  and  remains  there,  because  it  is  heavier  than  that 
of  sulphate  of  zinc,  which  is  placed  above. 

CHARGE  AND  MAINTENANCE. — The  zinc  being  put  in. 
place,  fill  the  jar  to  within  half  an  inch  of  the  top  of  the 
zinc  with  water  containing  one  tenth  of  a  saturated  solu- 
tion of  sulphate  of  zinc.  In  general,  when  the  solution 
of  sulphate  of  zinc  is  poured  in  the  water,  the  latter  be- 
comes slightly  cloudy,  which  is  the  result  of  the  presence 
of  a  small  quantity  of  carbonate  of  lime  in  the  water,  es- 
pecially if  well-water;  the  addition  of  the  sulphate  of 
zinc  brings  about  a  reciprocal  action  ;  carbonate  of  zinc  is 
formed,  and  sulphate  of  lime  is  precipitated.  But  this 
precipitate,  being  in  a  very  small  quantity,  remains  a  long 
time  in  suspension,  during  which  time  the  whole  liquid 
assumes  an  opaline  tint.  At  length  the  sulphate  of  lime 
falls  to  the  bottom  of  the  jar.  It  does  not  sensibly  alter 
the  action  of  the  battery. 

The  sulphate  of  copper  is  added  by  means  of  a  siphon. 
The  solution,  prepared  beforehand,  is  conducted  to  the 
bottom  of  the  jar  and  increased  until  the  water  is  within 

*  This  is  explained  by  a  local  action,  the  formation  of  a  cell  be- 
tween the  two  liquids  and  the  copper  wire.  It  will  be  seen  farther 
on  that  a  current  can  be  produced  under  these  circumstances,  and 
the  natural  result  is  that  the  copper  is  dissolved  in  one  of  the  liquids. 


120  TWO-LIQUID   BATTERIES. 

a  quarter  of  an  inch  of  the  top  of  the  zinc.  The  sul- 
phate of  copper  does  not  remain  separate  at  the  bottom 
of  the  jar ;  it  mingles  with  the  lower  part  of  the  rest  of 
the  liquid,  and  consequently  it  is  a  diluted  solution  and 
not  a  saturated  one,  which  surrounds  the  negative  elec- 
trode. We  have  already  said,  in  speaking  of  the  porous- 
jar  battery,  that  a  saturated  solution  presents  no  advan- 
tage and  only  renders  the  local  action  more  energetic. 

The  quantity  of  sulphate  mentioned  is  sufficient  for 
one  month.  A  too  great  weakening  of  the  solution  may 
be  recognized  by  the  discoloration  of  the  lower  stratum 
of  liquid. 

When  the  solution  of  sulphate  of  copper  is  again  add- 
ed, it  is  better  to  take  off  about  a  quarter  of  an  inch  from 
the  top  of  the  water,  unless  evaporation  has  already  low- 
ered the  water,  in  which  case  some  pure  water  should  be 
added,  in  order  to  reduce  the  concentration  of  the  sul- 
phate of  zinc. 

It  is  best  to  examine  the  battery  every  three  months ; 
but  if  it  is  properly  taken  care  of  from  month  to  month, 
it  need  only  be  thoroughly  cleaned  once  a  year.  When 
this  is  done,  the  deposits  formed  upon  the  surface  of  the 
zinc  should  be  scratched  off,  the  jars  washed,  and  the 
liquids  renewed  as  in  the  beginning. 

We  add  that  twenty-six  batteries,  eighteen  cells  in  each, 
distributed  in  as  many  stations,  caused  an  expense  of  fif- 
teen cents  yearly  for  each  cell.  This  result,  calculated 
upon  three  years'  experience,  has  the  value  of  practical 
information. 

LOCAL  ACTIONS  AND  LOST  WORK. — Daniell's  gravity 
battery  is  not  free  from  that  great  fault  that  we  have 
indicated,  which  consists  in  the  local  chemical  actions 
which  do  not  co-operate  in  the  production  of  elee- 


GEAVITY  BATTERIES.  121 

tricity,  and  which  even  take  place  when  the  circuit  is 
open. 

The  two  liquids,  one  above  the  other,  would  mingle 
extremely  slowly  if  it  were  not  for  several  causes,  which 
we  will  examine.  If  a  gravity  cell  be  closely  observed, 
the  formation  of  gaseous  bubbles  at  the  contact  of  the 
zinc,  and  even  upon  the  surface  of  the  copper  electrode, 
is  seen,  and  these  bubbles,  freeing  themselves  from  time 
to  time,  produce  an  agitation  of  the  liquid.  Indeed,  two 
distinct  currents  in  the  liquid  are  seen,  descending  on  one 
side  and  rising  upon  the  other,  which  brings  about  a  very 
slow  mingling  of  the  liquids.  We  will  again  have  occa- 
sion to  speak  of  these  bubbles  of  gas  and  their  effects ;  it 
suffices  for  the  present  to  observe  the  movement  they 
produce  in  the  liquid.  The  result  of  this  movement  is 
that  a  small  quantity  of  sulphate  of  copper  ascends  to  the 
top.  This  salt  decomposes  at  the  surface  of  the  zinc ; 
copper  is  deposited,  and  an  equivalent  quantity  of  zinc  is 
dissolved.  The  copper  generally  attaches  itself  to  the 
lower  part  of  the  zinc,  and  frequently  in  the  shape  of 
pendants  or  stalactites,  which  hang  below  the  zinc.  The 
longer  these  pendants  become  the  more  rapidly  they 
grow,  and  if  they  reach  the  level  of  the  sulphate  placed 
in  the  bottom  of  the  jar,  the  battery  becomes  rapidly  ex- 
hausted. It  is,  therefore,  very  advantageous  to  detach 
these  stalactites,  which  can  be  done,  when  the  battery  is 
examined,  by  sharp  taps  on  the  zinc.  The  zinc  should 
be  in  a  perfectly  horizontal  position;  for  if  one  side  were 
lower  than  the  other,  pendants  would  form  themselves 
rapidly  on  the  lower  side. 

RESISTANCE  OF  CALLAUD'S  CELL. — There  are  two  sizes 
of  Callaud's  cell  in  use,  one  of  which  is  much  larger  than 
the  other ;  but  the  separation  of  the  electrodes  balances 


122  TWO-LIQUID   BATTERIES. 

the  difference  in  the  dimensions,  and  the  two  cells  liavo 
sensibly  the  same  resistance. 

This  resistance  has  been  obseryed  to  vary  from  37  units 
at  the  beginning,  when  the  water  contains  very  little  sul- 
phate of  zinc,  to  51^-  units  after  23  days'  work ;  that  is, 
when  a  considerable  quantity  of  sulphate  of  zinc  has  been 
formed.  These  figures  confirm  that  which  we  have  pre- 
viously said  of  the  Daniell  gravity  cell ;  no  exact  figures 
even  for  batteries  of  well-determined  dimensions  can  be 
given ;  only  vague  limits  between  which  the  resistance 
varies  can  be  fixed  upon.  At  all  events,  Callaud's  cell 
should  be  considered  as  possessing  a  very  feeble  resist- 
ance, and  as  well  adapted  for  local  as  for  long  and  resist- 
ant circuits. 

APPLICATIONS    OF    CALLAUD'S    BATTERY. 

This  battery  was  not  very  extensively  used  by  the  Eng- 
lish, because  they  claimed  that,  to  work  well,  it  should 
not  be  moved  at  all.  This,  however,  should  not  be  exag- 
gerated, as  in  France  the  battery  is  placed  in  a  box  upon 
rollers.  The  box  remains  under  the  table  during  work, 
and  is  only  pulled  out  when  the  battery  is  to  be  examined 
or  recharged.  This  movement  has  no  sensible  effect  upon 
the  working  of  the  battery. 

It  has  been  adopted  in  Italy  with  a  slight  modification. 
The  glass  jar,  instead  of  having  the  shape  of  the  ordinary 
one,  is  compressed  in  the  middle,  thus  dividing  it  into 
two  compartments.  The  zinc  rests  upon  the  border  of 
this  partition.  The  diameter  of  the  jar  at  the  top  and 
bottom  is  four  inches,  and  that  of  the  middle  portion  is 
only  two  inches.  These  dimensions  would  seem  to  in- 
crease the  resistance,  without  presenting  any  counterbal- 


GRAVITY   BATTERIES.  123 

ancing  advantages.  The  dimensions  of  the  Italian  bat- 
tery are  smaller  than  those  of  the  French  model ;  but 
such  as  it  is,  it  has  for  several  years  given  great  satisfac- 
tion, as  much  on  account  of  its  constancy  as  on  account 
of  the  economy  and  facility  of  keeping  it  in  order. 

This  battery  is  very  extensively  employed  in  the  United 
States.  The  monthly  expense  of  keeping  in  order  600 
Callaud  cells,  distributed  in  three  batteries  which  supply 
ten  circuits,  is  about  $30. 

There  is  another  modification  in  use  in  the  United 
States,  to  which  Mr.  Lockwood,  its  author,  has  given  his 
name.  The  peculiarity  of  this  form  consists  in  the  use 
of  two  flat  helices  as  the  copper  electrode.  One  of  these 
helices  is  placed  at  the  bottom  of  the  jar,  and  the  other 
above  the  sulphate  of  copper.  This  disposition  certainly 
renders  the  resistance  of  the  battery  less.  Lockwood 
uses  crystals  of  sulphate  of  copper,  which,  according  to 
our  view,  uselessly  increases  the  cost  and  the  local  ac- 
tions. 

TKOUVfi-CALLAUD  BATTEEY. 

Trouve  arranged  a  Dan i ell  gravity  battery,  which  is 
extremely  cheap.  Trouve  had  in  view  the  application  of 
his  battery  to  medical  purposes — it  furnishes  a  continu- 
ous current — which  is  at  present  used  in  many  hospitals 
and  by  many  physicians.  It  could  also  be  very  wrell  em- 
ployed for  other  purposes.  The  glass  jar  is  4f  in.  high 
and  2f  in.  in  diameter.  The  zinc  is  held  upon  the  rim 
of  the  jar  by  being  bent  over  in  three  places  by  means  of 
pincers.  The  negative  element  consists  of  a  copper  wire 
in  the  shape  of  a  flat  helix,  which  rises  in  a  glass  tube  to 
the  top  of  the  jar.  The  connection  between  the  cells  is 
made  by  means  of  a  spiral  spring  at  the  end  of  the  wire 


124  TWO-LIQUID   BATTERIES. 

which  is  soldered  to  the  zinc,  and  to  which  is  fastened  the 
wire  forming  the  connection  of  the  adjoining  cell. 

This  battery,  shown  by  Fig.  30,  differs   but   slightly 


Fm.  30. 

from  the  one  we  have  described  above ;  but  it  is  very 
simple  in  arrangement,  and  on  account  of  its  small  di- 
mensions each  cell  costs  only  12  cents. 

MEIDIKGER'S  BATTERY. 

This  is  one  of  the  most  extensively  employed  batteries 
in  Germany.  It  has  been  tried  in  many  other  countries, 
but  has  been  finally  abandoned  for  the  following  reasons  : 
Its  cost  is  greater  than  ordinary  Daniell  or  Callaud  bat- 
teries ;  its  internal  resistance  is  also  greater,  and  it  occu- 
pies a  considerable  space. 

The  Meidinger  battery  (Fig.  31)  consists  of  a  large 
glass  jar,  A,  at  the  bottom  of  which  is  placed  a  cup,  d.  In 
this  latter  is  -the  negative  element,  formed  of  a  thin  leaf 
of  copper,  <?,  rolled  in  the  shape  of  a  cylinder,  from  which 
a  copper  wire  rises  in  a  gutta  percha  tube,  <7,  to  the  top  of 
the  vessel,  and  forms  the  positive  connection  of  the  cell. 

The  cylinder  of  zinc,  Z,  is  suspended  above,  as  shown  in 


GRAVITY   BATTERIES.  125 

the  cut,  and  descends  a  little  below  the  top  of  the  cop- 
per. The  two  jars  are  filled  with  liquid.  The  glass  tube 
A,  pierced  with  holes  at  the  bottom,  is  placed  in  the  cen- 
tre of  the  cell,  with  the  lower  part  in  the  cup ;  this  cen- 
tral tube  is  filled  with  sulphate  of  copper  crystals.  The 
sulphate  of  zinc,  being  lighter,  remains  above  the  dissolved 
sulphate  of  copper.  At  the  beginning,  in  order  to  in- 
crease the  conductivity,  magnesic  sulphate  is  put  in  the 


FIG.  31. 

water,  which  solution  has  greater  conductivity  and  is  less 
dense  than  that  of  sulphate  of  copper. 

The  advantages  of  this  battery  are  as  follows : 
1.  It  contains  a  large  quantity  of  water  which  is  re- 
quired to  dissolve  the  sulphate  of  zinc  formed.  In  order 
that  the  battery  may  work  a  long  time  without 'any  atten- 
tion, this  condition  is  very  essential.  We  will  see  far- 
ther on  that,  when  the  solution  of  sulphate  of  zinc  ap- 
proaches saturation,  it  becomes  more  dense  than  that  of 
copper,  and  that  consequently  the  relative  positions  of 
the  liquids  are  apt  to  change. 


126  TWO-LIQUID   BATTERIES. 

2.  The  deposits  of  copper  which  form  upon  the  sur- 
face or  hang  in  stalactites  from  the  lower  part  of  the  zinc 
fall  outside  of  the  centre  cup  and  thus  do  not  touch  the 
solution  of  sulphate  of  copper;  this  contributes  greatly 
to  the  cleanliness  and  good  condition  of  the  battery.     We 
have  seen  (in  speaking  of  Callaud's  battery)  that,  when 
these  stalactites  touch  the  solution  of  sulphate  of  copper, 
local  action  increases  rapidly  and  assumes  a  very  injurious 
intensity.     This  latter  inconvenience  is  avoided  in  Meidin- 
ger's  battery. 

3.  The  cover  which  closes  the  cell  and  which  is  neces- 
sary to  support  the  glass  tube  (sulphate  of  copper  reser- 
voir) almost  completely  prevents  evaporation. 

4.  A  first  inspection  will  show  whether  the  sulphate  of 
copper  is  used  up  or  not ;  the  electro-motive  force  is  kept 
up  until  the  last  crystal  has  disappeared  and  the  resist- 
ance rather  diminishes. 

Lately,  Meidinger  has  replaced  the  copper  with  lead. 
This  does  not  in  any  way  alter  the  nature  of  the  chemical 
action,  for  the  electrode  soon  becomes  covered  with  the 
deposit  of  copper.  The  copper  wire  which  serves  as  the 
connection  is  also  replaced  by  a  strip  of  lead,  which  in- 
deed needs  no  protection,  for  lead  is  not  attacked  by  the 
liquids  which  enter  into  the  composition  of  the  battery. 

The  only  advantage  in  the  substitution  of  lead  for  cop- 
per is  that  it  reduces  the  cost  of  the  battery. 

"We  have  already  spoken  of  the  disadvantage  in  keep- 
ing the  solution  in  a  state  of  saturation  ;  we  find  a  confir- 
mation of  our  opinion  in  the  following  fact :  The  ad- 
ministration of  Berlin  recommends  not  to  recharge  the 
cells  until  the  last  crystal  of  the  preceding  charge  has 
disappeared  and  not  to  put  in  too  large  a  quantity  of  sul- 
phate of  copper. 


GEAVITY   BATTERIES.  127 

A  commission  chosen  by  this  administration  observed, 
also,  that  the  economical  coefficient  diminished  when  the 
cells  were  too  frequently  charged  or  with  too  great  a  quan- 
tity. 

According  to  our  view,  there  should  have  been  a  com- 
plete suppression  of  crystals.  We  will  soon  see  that  the 
commission  arrived  at  a  contrary  conclusion  ;  it  preferred, 
it  would  seem,  to  sacrifice  the  economy  of  the  material 
and  to  diminish  the  work  of  the  operators. 

Dr.  Dehms  reports  the  resistance  of  Meidinger's  ele- 
ment as  varying  from  4  to  9  of  Siemen's  units,*  according 
to  the  models. 

MEIDINGER'S  FLASK  BATTERY. 

Instead  of  the  interior  tube  reservoir,  Meidinger  has 
finally  adopted  a  large  exterior  flask  as  reservoir  for  the 
crystals  (Fig.  32).  This  form  has  been  in  use  a  long  time 
in  Bavaria  and  Germany,  where  it  was  recommended  for 
branch  telegraph  offices  and  for  the  following  reasons : 

1.  In  all  branch  offices  (in  Northern  Germany)  contin- 
uous currents  are  employed ;  the  consumption  of  the  bat- 
tery is  therefore  considerable,  and  if  the  labor   of  fre- 
quently renewing  the  elements  is  to  be  spared,  a  battery 
should  be  adopted  which  contains  a  large  quantity  of  ma- 
terial.    This  is  found  in  the  battery  in  question,  as  the 
flask  holds  two  pounds  of  sulphate  of  copper. 

2.  The  disappearance  of  the  charge  of  sulphate  of  cop- 
per is  here  more  plainly  seen  than  in  the  other  model, 
and  cannot  escape  the  most  rapid  glance. 

3.  In  these  branch  offices  the  battery  is  rarely  made  to 

*  A  Siemen's  unit  is  equal  to  the  resistance  offered  by  one  metre  of 
mercury  whose  sectional  area  is  one  millimetre. 


128  TWO-LIQUID   BATTEEIES. 

work  simultaneously  upon  several  lines  ;  therefore  its  re- 
sistance, which  is  considerable  (10  of  Siemen's  units  to 
each  cell  of  the  approved  form),  presents  but  little  incon- 
venience. 

Under  these  two  forms,  Meidinger's  battery  is  employed 


FIG.  32. 

in  the  railway  and  state  telegraph  services  of  Russia,  al- 
most to  the  exclusion  of  all  others. 

The  batteries  are  generally  left  one  year  without  care, 
in  some  instances  fourteen  months.  But  in  offices  where 
there  is  a  very  active  service,  the  sulphate  of  copper  is 
renewed  every  four  or  six  months. 

KRUGER'S  BATTERY. 

This  is  a  battery  said  to  have  advantages  over  other  bat- 
teries without  the  porous  jar.  The  zinc  is  placed  as  in 
Callaud's  ;  but  the  copper  has  the  form  of  a  hollow  cylin- 
der, and  is  placed  vertically  in  the  jar  and  has  the  same 


GRAVITY   BATTERIES.  129 

height.  The  cylinder  is  made  of  a  very  thin  piece  of 
copper,  cut  longitudinally  at  the  bottom  in  six  places ; 
the  divisions  thus  formed  are  bent  outward  and  hold  the 
cylinder  in  the  centre  of  the  jar.  There  are  also  three 
pegs  fastened  in  the  zinc,  which  serve  to  keep  the  copper 
cylinder  in  place. 

If  sulphate  of  'copper  crystals  are  added,  they  are  placed 
in  the  copper  cylinder  and  the  solution  formed  remains  at 
the  bottom  of  the  jar. 

This  disposition  costs  less  than  that  of  Meidinger,  and 
produces  a  battery  with  much  less  resistance ;  in  this  re- 
spect it  is  preferable  to  Callaud's,  but  costs  more. 

We  know,  however,  from  good  authority,  that  this 
battery  presents  a  grave  inconvenience.  The  copper  be- 
comes eaten  at  the  line  of  separation  of  the  two  liquids, 
and  at  the  end  of  a  certain  time  it  breaks.  It  will  be  re- 
membered that  we  mentioned,  when  speaking  of  Callaud's 
battery,  the  necessity  of  protecting  with  gutta-percha  the 
copper  wire  which  traversed  the  liquids  and  served  as  the 
connection. 

This  inconvenience  could  be  avoided  by  substituting 
lead  for  the  copper,  as  Meidinger  sometimes  does. 

In  the  first  edition  of  this  work  we  expressed  the  opin- 
ion that  the  portion  of  copper  which  is  not  immersed  in 
the  solution  of  sulphate  of  copper  tends  to  increase  the 
internal  conductivity  of  the  element,  although  it  takes 
no  part  in  the  regular  chemical  action  which  produces  the 
current.  Since  then,  Mr.  G.  d'Infreville  has  sent  us  the 
very  interesting  results  of  his  experiments  upon  this  sub- 
ject. He  has  found  that  this  disposition  causes  a  diminu- 
tion in  the  electro-motive  force.  This  will  not  seem  sur- 
prising to  physicists,  for  they  will  readily  understand  that 
in  Kruger's  or  any  analogous  battery  the  circuit  becomes 


130  TWO-LIQUID   BATTERIES. 

closed  by  the  sulphate  of  zinc  at  the  top ;  a  constant  de- 
rived current  is  thus  produced,  and  consequently  the  dif- 
ference of  potential  is  diminished  between  the  electrodes. 


SIK  WILLIAM  THOMSON'S  BATTEEY. 

This  illustrious  physicist  invented  a  very  original  dis- 
position of  the  Daniell  gravity  battery.  The  elements  are 
piled  up  one  upon  another  as  in  Volta's  column  battery 
or  as  in  Marie  Davy's  sulphate-of-lead  battery. 

These  elements  (Fig.  33)  consist  of  wooden  trays,  lined 


FIG.  33. 

on  the  inside  with  lead  to  make  them  water-tight.  At 
the  bottom  of  each  tray  is  placed  a  thin  plate  of  copper. 
In  the  four  corners  of  this  square  tray  are  little  blocks  of 
wood  which  support  the  zinc  electrode.  This  latter  has 
the  singular  form  of  a  gridiron,  having  its  bars  very  close, 
but  still  leaving  space  enough  between  for  the  circulation 
of  the  liquid.  The  feet  of  this  gridiron  arc  turned  up- 
wards, supporting  the  cell  above. 

In  some  instances  the  zinc  is  wrapped  in  parchment 


GEAVITY   BATTEEIES.  131 

paper,  thus  constructing  a  porous  jar  which  prevents  the 
mingling  of  the  liquids ;  this  may,  however,  well  be  dis- 
pensed with. 

The  connection  between  one  cell  and  the  following  one 
is  simply  obtained  by  their  weight,  which  presses  the  lead 
on  the  bottom  of  each  tray  upon  the  four  corners  of  the 
zinc  below. 

Care  must  be  taken  in  charging  the  cells,  to  place  them 
in  a  perfectly  horizontal  position ;  this  can  be  easily  as- 
certained by  pouring  some  water  in  the  tray  and  observ- 
ing if  it  spreads  equally  over  the  bottom. 

The  sole  advantage  of  this  form  is  the  feeble  resistance 
it  gives  to  the  cells.  It  is  used  as  local  battery  in  the 
submarine  telegraphs,  where  Sir  William  Thomson's 
"  Siphon  Recorder "  is  at  work.  "We  are  informed  that 
it  is  also  employed  in  Russia,  and  has  indeed  been  applied 
for  electric  light  purpose. 

The  battery  should  be  charged  with  a  solution  of  sul- 
phate of  zinc,  whose  density  is  1.10  and  the  sulphate  of 
copper  crystals  are  placed  as  regularly  as  possible  all 
around  and  at  the  bottom  of  the  tray. 

Scarcely  more  than  eight  or  ten  cells  can  be  piled  up 
in  one  column,  and  a  series  of  these  columns  are  con- 
nected by  very  large  conductors.  If  the  battery  is  used 
in  delicate  experiments  or  for  the  working  of  the 
"  Siphon  Recorder,"  it  imist  be  constantly  watched,  and 
a  little  of  the  sulphate  of  zinc  solution  taken  out  daily 
and  replaced  with  pure  water.  If  possible,  the  density 
of  the  liquid  should  be  kept  between  1.30  and  1.10 ;  for 
that  purpose  it  should  be  measured  from  time  to  time 
with  an  hydrometer. 

The  circuit  of  the  battery  should  always  be  closed,  in 
order  to  avoid  the  deposit  of  copper  upon  the  zinc.  It 


132  TWO-LIQUID   BATTEEIES. 

is  advisable  when  the  battery  is  not  in  use  to  keep  it  in 
short  circuit,  'so  that  the  sulphate  of  copper  may  be 
rapidly  exhausted. 

It  is  perhaps  a  good  idea  to  measure,  now  and  then, 
the  electro-motive  force  of  each  series  and  of  each  cell 
separately.  When  one  cell  is  found  to  have  lost  much, 
on  account  of  the  deposit  of  copper  upon  the  zinc,  it 
should  either  be  taken  away  entirely  or  placed  in  short 
circuit,  to  get  rid  of  the  useless  resistance  it  introduces 
into  the  circuit. 

Sir  William  Thomson  has,  besides,  given  an  inverse 
form  to  his  battery,  upon  the  basis  that  a  saturated  solu- 
tion of  sulphate  of  zinc  has  a  density  of  1.44,  whereas  a 
saturated  solution  of  sulphate  of  copper  has  a  maximum 
density  of  1.18 ;  the  sulphate  of  zinc  is  below  and  the 
sulphate  of  copper  is  above,  the  contrary  of  that  which 
prevails  in  all  preceding  batteries.  We  have  not  been 
able  to  obtain  any  notes  that  the  eminent  author  may 
have  published  upon  the  subject,  and  do  not  therefore 
know  his  motives  for  this  reversed  form.  We  only  know 
that  it  is  practically  inconvenient,  and  presents  the  fol- 
lowing fault,  viz.,  that  reduced  copper  falls  upon  and 
finally  covers  the  zinc.  It  is  possible,  however,  that  this 
reversed  form  possesses  great  advantages  for  special  cases. 

The  principle  of  this  form  deserves  notice.  It  is  seen 
that  if,  in  ordinary  gravity  batteries,  the  sulphate-of-zinc 
solution  is  permitted  to  approach  or  to  arrive  at  satura- 
tion, the  two  liquids  are  no  longer  separated  by  their 
difference  in  density  in  the  desired  manner ;  the  result  is 
that  the  battery  works  badly  and  there  is  considerable 
waste. 


GKAVITY   BATTERIES.  133 


ELECTRO-MOTIVE   FORCE  OF  THE  DANIELL 
GRAVITY  BATTERY. 

At  first  it  would  seem  that  the  electro-motive  force  of 
the  Daniell  battery  ought  to  be  the  same,  with  or  with- 
out the  porous  jar.  The  results  of  all  measurements 
show,  however,  the  superiority  of  the  gravity  battery. 
One  might  believe  that  these  differences  arise  from 
errors  of  observation ;  but  we  have  assured  ourselves  by 
a  direct  comparison  made  by  the  method  of  opposition 
that  the  electro-motive  force  of  gravity  cells  is  the  same 
in  models  differing  widely  from  each  other,  and  that  it  is 
much  greater  than  that  of  a  cell  with  the  porous  jar. 

This  is  a  peculiarity  difficult  to  explain,  unless  a  feeble 
polarization  at  the  surface  of  the  porous  jar  be  admitted. 

It  must  undoubtedly  be  placed  with  that  other  fact  of 
which  we  have  spoken ;  viz.,  the  electro-motive  force  of 
Daniell's  porous-jar  element  is  very  inferior  to  its  normal 
value  when  it  is  first  mounted  and  when  the  imbibition 
of  the  porous  jar  is  not  yet  complete. 


CHAPTER  III. 
GENERAL  REMARKS  UPON  DANIELL  BATTERIES. 


AMALGAMATION  OF  ZINC  IN  THE  DANIELL 
BATTERY. 


have,  from  the  beginning  of  this  work,  shown  the 
advantages  of  amalgamated  zinc  over  commercial  zinc 
when  immersed  in  dilute  sulphuric  acid. 

When,  therefore,  a  Daniell  battery  is  charged  with 
dilute  sulphuric  acid,  there  is  a  great  advantage  in  the 
use  of  amalgamated  zinc  ;  but  to-day  the  acid  is  mostly 
suppressed  and  replaced  by  sulphate  of  zinc.  It  is  gen- 
erally believed  that  it  is  still  advisable  in  this  case  to 
amalgamate  the  zinc,  but  we  have  informed  ourselves  as 
to  the  subject,  and  find  that  the  addition  of  mercury  is 
rather  injurious  than  useful. 

We  have  ta,ken  several  cells,  one  having  amalgamated 
zinc,  joined  them  in  intensity,  and  allowed  them  all  to 
undergo  the  same  alternatives  of  rest  and  action.  At 
the  end  of  fifteen  days  it  was  found  that  the  local  action 
had  been  much  greater  upon  the  amalgamated  zinc  than 
upon  the  others  ;  that  is,  the  deposit  upon  the  surface  of 
the  zinc  and  at  the  bottom  of  the  jar  was  more  abundant 
in  the  amalgamated  cell. 

To  confirm  this  result  we  have  made  the  following 
experiment,  like  that  of  De  La  Hive  :  We  put  a  piece 


EEMAKKS   UPON   DANIELL   BATTERIES.  135 

of  well-amalgamated  zinc  in  a  solution  of  sulphate  of 
copper  ;  the  attack  took  place  immediately  and  rapidly  ; 
in  twenty  minutes  all  the  sulphate  of  copper  was  decom- 
posed. 

These  experiments  possess  no  other  interest,  however, 
than  that  of  justifying  the  general  practice  adopted  by 
those  who  use  the  Daniell  battery  without  free  sulphuric 
acid  ;  that  is,  in  the  electric  telegraph  and  analogous  appli- 
cations. 

Experiments  of  Jules  Regnauld  give  the  following 
figures  for  the  electro-motive  forces  of  the  batteries  in 
question : 

Pure  zinc,  sulphate  of  zinc,  sulphate  of  copper,  copper 175 

Amalgamated  zinc,  sulphuric  monohydrate,   1  vol. 

Water,  10  vol. ;  sulphate  of  copper,  copper 179 

It  is  therefore  clear  that  the  use  of  amalgamated  zinc 
in  acidulated  water  occasions  a  slight  increase  of  the  elec- 
tro-motive force ;  this  superiority,  however,  which  is  less 
than  2J-  per  cent,  has  but  little  practical  interest. 


COFFEE-PLATING. 

The  study  of  Dani  ell's  battery  has  led  to  the  creation 
of  a  vastly  important  industry ;  namely,  that  of  copper- 
plating.  Its  object  is  the  reproduction  in  copper  of 
artistic  or  mechanical  models,  typographic  blocks,  med- 
als, bas-reliefs,  statuettes,  etc.  etc. 

Jacobi  in  Russia,  and  Spencer  in  England,  having 
observed  that  the  copper  which  is  deposited  upon  the 
copper  electrode  was  so  fine  as  to  reproduce  the  smallest 
irregularities  of  surface  of  that  electrode,  decided  to 
make  use  of  this  process  of  moulding,  and  they  have 


136  TWO-LIQUID   BATTEEIES. 

shown  its  great  utility.  The  extreme  facility  of  the  pro- 
cess renders  it  accessible  to  every  one,  and  consequently 
its  use  has  spread  with  infinite  variations. 

We  shall  not  enter  upon  the  details  of  this  process, 
but  only  show  the  most  simple  method  of  copper-plating, 
which  consists  in  the  use  of  a  large  Daniell  cell  with  the 
porous  jar.  The  porous  jar  contains  the  amalgamated  zinc 
immersed  in  well-acidulated  water.  In  the  outside  jar, 
which  is  comparatively  much  larger,  is  a  saturated  solution 
of  sulphate  of  copper  and  electrodes  formed  of  pieces  of 
gutta-percha  moulded  upon  the  model  (medal  or  wood- 
engraving).  To  the  surface  of  these  gutta-percha  moulds 
is  imparted  a  conductive  quality  by  means  of  an  im- 
palpable powder  of  plumbago  spread  upon  it  with 
brushes.  An  exterior  conductor  joins  the  zinc  to  the 
negative  electrode.  The  deposit  commences  directly  and 
is  very  slow  at  first  upon  the  plumbago,  but  as  the  copper 
accumulates  the  process  advances  at  a  more  rapid  rate. 

All  the  figures  which  illustrate  this  book  were  first  en- 
graved on  wood,  then  moulded  in  gutta-percha,  and  finally 
reproduced  in  copper,  in  the  manner  we  have  just  de- 
scribed. It  is  with  these  electrotypes  that  the  impressions 
were  made,  and  it  is  the  process  generally  employed. 

It  is  seen  that  the  battery  which  produces  this  indus- 
trial deposit  is  one  of  a  single  cell,  and  that  the  deposit 
takes  place  in  this  single  cell. 

It  is  impossible  to  imagine  any  more  simple  process ; 
but  it  is  not  as  economical  as  it  might  at  first  appear,  be- 
cause, to  extract  a  given  weight  of  copper  from  the  sul- 
phate, and  deposit  it  upon  the  mould,  there  must  be  con- 
sumed an  equivalent  weight  of  zinc  and  sulphuric  acid, 
without  counting  the  mercury  lost  in  the  manipulations. 


REMARKS    UPON   DANIELL   BATTERIES. 


IKREGULAKITY  OF  THE  CHEMICAL  ACTION 
IN  DANIELL'S  BATTEEIES. 

We  said  in  the  beginning  that  the  chemical  action  in 
the  Daniell  battery  was  limited  to  the  dissolving  of  the 
zinc,  the  substitution  of  zinc  for  the  copper  in  the  sul- 
phate, and  the  deposit  of  copper  upon  the  conducting 
electrode.  That  is  indeed  the  theoretical  and  principal  ac- 
tion ;  but  it  is  not  the  only  one.  We  have  shown  in  the 
foregoing  that  there  are  local  actions  in  the  neighborhood 
of  the  zinc  and  a  deposit  of  copper  upon  the  zinc. 

But  that  is  not  yet  all.  If  the  Daniell  battery  be  closely 
examined  (Callaud's  battery  is  well  suited  to  this  exami- 
nation, because  one  can  see  everything  that  goes  on  in- 
side), a  continual  formation  of  gaseous  bubbles  at  the  sur- 
face of  the  zinc,  and  indeed  upon  the  copper  electrode, 
is  seen. 

As  to  the  freeing  of  hydrogen  from  the  zinc,  the  fol- 
lowing is  the  simple  explanation  : 

This  zinc  is  immersed  in  sulphate  of  zinc.  The  zinc 
not  being  pure,  small  voltaic  cells  form  themselves  at  its 
surface,  and  consequently  the  water  is  decomposed  and 
hydrogen  given  off. 

The  explanation  is  analogous  concerning  the  coppei 
electrode;  the  different  parts  of  this  electrode  are  im- 
mersed in  unequally  saturated  portions  of  the  sulphate  of 
copper,  or  even  in  portions  containing  sulphate  of  zinc  ; 
a  voltaic  cell  is  thus  constituted  between  the  two  liquids 
and  the  single  electrode.  We  will  return,  at  the  end  of 
this  work,  to  identical  electrode  batteries,  when  all  doubts 
the  reader  may  here  have  will  be  dispelled. 

There  is  less  freeing  of  hydrogen  from  the  copper  than 


138  TWO-LIQUID   BATTERIES. 

from  the  zinc,  no  doubt  because  the  voltaic  cells  formed 
have  a  much  smaller  electro-motive  force. 

Whatever  the  truth  of  these  explanations  may  be,  the 
fact  of  the  freeing  of  hydrogen  is  not  to  be  doubted. 
Large  gaseous  bubbles  are  seen  attached  to  the  surface  of 
the  zinc,  and  in  perfect  stillness  they  may  be  heard  to 
free  themselves  now  and  then  and  rise  to  the  surface, 
making  a  slight  noise  as  they  explode. 

These  abnormal  actions  are  not  the  only  ones  that  take 
place  in  the  Daniell,  but  they  are  the  most  important. 


CHAPTEE  IV. 
BATTERIES  DERIVED  FROM  THE  DANIELL. 

BY  replacing  the  copper  in  the  Daniell  battery  by  some 
other  metal  and  the  sulphate  of  copper  by  the  sulphate 
of  that  metal,  batteries  possessing  qualities  analogous  to 
those  of  the  Daniell  may  be  made. 

Several  of  them  have  a  practical  interest,  but  we  will 
at  first  mention  two  that  can  only  serve  in  laboratories. 

The  cadmium  battery  is  formed  of  zinc,  sulphate  of 
zinc,  sulphate  of  cadmium,  and  cadmium.  Its  electro- 
motive force  is  0.31 ;  that  is,  thirty-one  hundredths  of 
the  unit,  or,  to  use  round  numbers,  one  third  of  the 
Daniell  battery.  Such  are,  at  least,  the  figures  given  by 
M.  Jules  Regnauld. 

The  aluminium  battery  is  still  more  feeble :  zinc,  sul- 
phate of  zinc,  aluminic  sulphate,  and  aluminium.  The 
electro-motive  force  is  0.2,  or  one  fifth  of  that  of  the 
Daniell. 

The  tables  at  the  end  of  this  work  will  show  other  com- 
binations, which  are  of  no  interest  here. 

To  our  knowledge,  no  one  has  ever  tried  the  zinc,  sul- 
phate of  zinc,  sulphate  of  iron,  and  iron  battery  ;  a  study 
of  it  would  undoubtedly  be  very  interesting. 

The  batteries  which  we  will  now  study  have  indeed  the 
Daniell  for  model,  but  they  possess  a  striking  peculiarity ; 
viz.,  the  depolarizing  salt  is  almost  insoluble,  which  gives 
rise  to  certain  interesting  results. 


140  TWO-LIQUID  BATTERIES. 

MARlfi  DAVY'S  SULPHATE  -  OF  -  MERCUEY 
BATTERY. 

Of  all  batteries  having  the  Daniell  for  model,  the  most 
interesting  is  that  proposed  by  Marie  Davy.  It  has  been 
extensively  employed,  and  is  still  used  in  many  cases. 

Let  us  substitute,  in  the  Daniell,  sulphate  of  mercury 
for  sulphate  of  copper,  and  carbon  fo*r  copper,  and  we 
will  have  the  new  battery.  In  truth,  if  we  had  strictly 
followed  the  model,  we  should  have  replaced  the  copper 
by  mercury ;  but  the  liquid  nature  of  this  metal  and  its 
high  price  have  caused  the  preference  of  a  carbon  elec- 
trode. Besides,  the  action  of  the  battery  producing  the 
reduction  of  the  sulphate  and  the  deposit  of  metallic 
mercury  upon  the  negative  or  conducting  electrode,  the 
difference  disappears  in  time,  and  there  is  in  reality  an 
electrode  of  mercury  in  which  is  immersed  a  piece  of 
carbon.  It  has  been  proved  that  the  electro-motive  force 
is  not  changed  by  the  suppression  of  the  carbon  and  the 
use  of  mercury,  provided  the  latter  is  pure. 

Fig.  34  represents  the  form  that  Marie  Davy  has  given 
to  his  cell.  The  zinc  is  a  hollow  cylinder  placed  in  the 
glass  jar  around  the  porous  jar ;  this  latter  contains  the 
carbon  electrode  surrounded  with  a  liquid  paste  of  sul- 
phate of  mercury.  The  carbon  is  capped  with  copper, 
to  which  is  soldered  a  strip  of  the  same  metal,  connected 
with  the  zinc  of  the  adjoining  cell.  The  carbon  may  also 
be  capped  with  lead,  and  the  connection  made  in  the 
same  way.  In  either  case  it  is  better  to  first  dip  the  top 
of  the  carbon  in  a  bath  of  paraffin,  in  order  to  fill  up  all 
the  pores  so  that  no  liquid  may  rise  by  capillarity  and  at- 
tack the  lead  or  copper. 


BATTERIES   DERIVED   FROM   THE   DANIELL.      141 

The  chemical  action  in  this  battery  is  precisely  analo- 
gous to  that  in  the  Daniell.  The  sulphate  of  mercury  is 
reduced,  an  equivalent  quantity  of  sulphate  of  zinc  is 
formed,  the  zinc  is  dissolved,  and  metallic  mercury  is 
deposited  in  the  porous  jar,  either  upon  the  surface  of 
the  carbon-electrode  or  in  the  mass  of  the  sulphate  of 


mercury. 

In     the    French    Telegraph,    suboxide 


of 


mercury 


FIG.  34 

(SO3Hg2O)  is  generally  used ;  consequently  two  equiva- 
lents of  mercury  are  set  free  for  one  of  zinc  dissolved. 

But  there  are  other  sulphates  that  may  also  be  em- 
ployed. 

The  sulphate  of  protoxide  (HgO,SO3)  is  frequently 
used  for  medical  purposes.  This  salt  presents  a  singular 
peculiarity :  coming  in  contact  with  water,  it  decomposes 
into  two  salts,  the  one  basic  and  but  very  little  soluble ; 


142  TWO-LIQUID   BATTERIES. 

the  other  acid,  very  soluble,  which  has  not  as  yet,  to  our 
knowledge,  been  analyzed.  The  first  salt  has  a  yellow  ap- 
pearance, whose  formula  is  3(HgO)  SO3 ;  it  is  therefore 
a  tribasic  salt. 

Marie  Davy's  batteries  may  be  charged  with  mono- 
basic sulphate  of  protoxide  (HgOSO3),  and  even  with 
the  tribasic  sulphate  alone  [3  (HgO)  SO3],  and  we  are  as- 
sured that  these  two  batteries  have  sensibly  the  same 
electro-motive  force  as  that  in  which  sulphate  of  suboxide 
(HgaOSOa)  is  used. 

It  is  said  that  this  last  salt  ought  to  be  preferred  to 
the  others,  because  the  tribasic  salt,  mentioned  above, 
breaks  the  porous  jars  by  its  little  solubility ;  but  admit- 
ting this,  the  two  salts  of  protoxide  can  very  well  be  used 
in  gravity  batteries,  of  which  we  shall  speak  further  on. 

Marie  Davy's  battery  presents  the  following  advan- 
tages : 

1.  It  has  an  electro-motive  force  very  much  superior  to 
that  of  Daniell ;  it  is  represented  by  1.5. 

2.  The   slight  solubility  of  the  sulphate   of  mercury 
causes  but  a  very  slow  diffusion  in  the  outer  liquid ;  the 
result  is  that  the  local  actions  and  the  waste  are  not  so 
important  as  in  the  Daniell  battery. 

3.  The  mercury  which  is  deposited  upon  the  zinc  by 
local  action,  and  without  any  corresponding  production  of 
electricity,  amalgamates  the  zinc,  or  keeps  up  its  amalga- 
mation, which  is  very  useful  and  prevents  the  waste  of 
the  sulphuric  acid  if  it  is  used  in  the  outside  jar. 

The  faults  of  this  battery  are  as  follows : 
The  sulphate  of  mercury  is  a  violent  poison ;  the  price 
of  this  salt  is  high  and  very  variable,  as  the  price  of  the 
mercury  itself.    Finally,  it  is  apt  to  weaken  under  certain 
circumstances,  as  we  will  show  in  detail. 


BATTEKIES   DERIVED   FROM   THE  DANIELL.     143 


WEAKENING  OF  THE    SULPHATE -OF - 
MERCURY  BATTERY. 

When  Marie  Davy's  battery  is  employed  for  the  tele- 
graph or  any  intermittent  service,  no  variation  in  the 
electro-motive  force  is  noticed,  and  the  battery  may  be 
regarded  as  constant.  But  if  the  circuit  remain  continu- 
ously closed,  or  if  the  intervals  of  its  being  open  are  too 
short,  a  diminution  in  the  intensity  is  observed.  This 
diminution  is  the  result  of  several  causes.  We  will  com- 
mence by  speaking  of  one  of  them,  which  we  have  not 
yet  met  in  the  course  of  this  study. 

The.  special  characteristic  of  the  Marie  Davy  battery, 
when  compared  with  the  Daniell,  is  the  insolubility  of  the 
mercurial  salt.  It  must,  however,  be  noted  that  the  sul- 
phate of  mercury  is  not  altogether  insoluble,  but  very 
little  soluble,  and  it  would  be  a  great  mistake  to  call  the 
battery  which  we  are  now  studying  a  single  liquid  bat- 
tery. There  are,  in  reality,  two  liquids,  the  solution  of 
sulphate  of  zinc  and  that  of  sulphate  of  mercury.  In 
1860  we  made  the  following  experiment : 

A  solution  of  sulphate  of  mercury  was  prepared  and 
well  filtered,  so  that  no  traces  of  undissolved  salt  might 
remain;  then  a  battery  charged  with  zinc,  sulphate  of 
zinc  dissolved,  sulphate  of  mercury  dissolved,  and  carbon. 
This  battery  had  exactly  the  same  electro-motive  force  as 
that  of  an  ordinary  Marie  Davy  battery  containing  100 
grammes  (or  more)  of  paste  of  mercurial  salt. 

The  comparison  was  made  by  opposition  with  a  very 
sensitive  galvanometer  ;  there  was,  therefore,  no  room  for 
any  doubt. 

But  if  this  filtered   solution  of  sulphate  of  mercury 


144  TWO-LIQUID   BATTERIES. 

battery  were  called  upon  to  furnish  a  current,  it  would  be 
seen  to  weaken  very  rapidly,  which  is  easily  under- 
stood. 

The  very  small  quantity  of  mercurial  salt  dissolved  was 
soon  exhausted,  and  depolarization  was  no  longer  effected ; 
from  that  moment  it  was  simply  a  single-liquid  battery 
which  polarized  promptly. 

That  is,  in  reality,  what  may  be  expected  in  all  batter- 
ies containing  an  only  slightly  soluble  depolarizing  salt, 
when  they  furnish  a  large  quantity  of  electricity.  If  the 
consumption  of  the  dissolved  mercurial  salt  is  more  rapid 
than  the  dissolving  of  the  salt  in  the  liquid,  the  solution 
of  course  weakens,  and  finally  does  not  act  at  all,  so  that 
the  battery  is  no  longer  a  two-liquid  battery  but  a  single- 
liquid  one,  and  consequently  becomes  weakened  by  polar- 
ization. 

The  above  constitutes  the  first  period  of  the  action  of 
the  battery.  We  will  now  examine  the  second.  As  soon 
as  the  battery  is  reduced  to  a  single  liquid  it  becomes  sub- 
ject to  polarization.  This  polarization  is  subject  to  the 
rules  that  we  have  indicated  in  the  first  part  of  this  wrork. 
It  depends  upon  the  intensity  of  the  current,  and  assumes 
a  much  greater  value  when  the  cell  in  question  is  polar- 
ized by  the  current  furnished  by  other  cells  joined  with 
it  in  intensity.  It  depends  upon  the  dimensions  of  the 
cell  and  of  the  elements.  And  it  depends,  finally,  upon 
the  length  of  time  of  the  experiment  and  upon  the  resist- 
ance of  the  circuit. 

This  is  the  same  phenomenon  that  we  have  already 
studied  several  times.  But  a  third  period  has  been  ob- 
served in  this  battery,  and  also  in  others.  When  a  cell 
becomes  extremely  polarized  it  loses  all  its  force,  and  then 
electrolysis  of  the  sulphate  of  zinc  takes  place.  This  salt 


BATTEEIES   DERIVED   FROM   THE   DANIELL.     145 

is  decomposed,  zinc  is  deposited  upon  the  carbon,  and, 
coming  in  contact  with  the  mercury  there,  the  two  unite 
and  form  one  amalgam  of  zinc,  which  is  at  first  positive, 
but  which  soon  becomes  negative,  as  compared  with  the 
zinc,  when  the  quantity  dissolved  in  the  mercury  becomes 
considerable.  Thus  is  formed  a  zinc  amalgam-of-zinc 
cell  whose  poles  are  contrary  to  those  of  the  original  cell. 
In  other  words,  the  poles  are  reversed  in  this  third  period. 
We  have  previously  pointed  out  an  analogous  action  as 
taking  place  in  the  salt-water  battery,  and  it  is  probable 
that  the  cause  is  the  same.  Now  this  reversing  of  the 
poles  and  the  extreme  polarizations  do  not  take  place  in 
the  general  operations  of  the  telegraph,  because  the  cells 
are  only  used  intermittingly  and  have  time,  during  the 
intervals  of  repose,  to  depolarize. 

It  is  understood  that  the  smaller  the  cells  and  the  less 
mercurial  salt  they  contain,  the  more  rapid  the  weakening 
of  the  solution  of  sulphate  of  mercury.  Therefore  cells 
4f  inches  high  are  recommended.  Cells  of  these  dimen- 
sions, however,  cost  a  great  deal,  and  in  general  cells  3^ 
inches  high  are  adopted,  which  are  all  that  is  necessary  for 
unimportant  telegraph  offices. 

Care  should  be  taken  that  the  level  of  the  liquids  re- 
main sensibly  the  same  in  cells  joined  in  intensity,  be- 
cause  if  in  one  the  level  is  notably  lowered,  it  is  as  if  this 
cell  had  become  smaller ;  the  dissolved  mercurial  salt  of 
this  cell  would  become  rapidly  exhausted  and  the  cell 
would  polarize. 


146 


TWO-LIQUID   BATTERIES. 


SULPHATE  -  OF  -  MERCUK Y 
TEKY. 


GEAYITY  BAT- 


A  French  physicist  arranged  sulphate-of-mercury  cells 
after  the  model  of  Callaud's  battery,  and  succeeded  very 
well  by  adding  to  the  mass  of  mercurial  salt  fragments  of 
crushed  gas-retort  carbon  (volume  for  volume).  This  car- 


FIG. 


bon  produces  a  kind  of  drainage  and  prevents  the  salt 
from  becoming  too  compact,  which  in  ordinary  batteries 
renders  the  dissolution  slower  than  is  proper. 


BATTERIES   DERIVED    FROM   THE   DANIELL.     147 

We  believe  that  the  tribasic  salt  of  sulphate  of  protox- 
ide of  mercury,  which  is  less  costly  than  the  other  mer- 
curial sulphates,  might  well  be  employed  in  batteries  of 
this  kind. 

TROUYfi'S  EEYERSIBLE   BATTERY. 

Trouve  arranged,  with  a  view  to  medical  purposes,  a 
battery  which  presents  incontestable  advantages  for  cer- 
tain uses. 

A  cell  of  this  battery  is  shown  in  Fig.  35.  The  out- 
side jar  is  a  cylinder  of  ebonite,  closed  at  both  extremi- 
ties by  ebonite  screw  tops.  At  the  upper  part  is  seen 
the  zinc  in  the  shape  of  a  small  cylinder  fixed  in  the 
middle,  to  which  is  attached  a  wire  that  passes  through 
the  top  and  constitutes  the  negative  connection  of  the 
cell.  The  carbon  is  cylindrical  and  surrounds  the  zinc. 
The  liquid,  formed  of  water  and  of  sulphate  of  protoxide 
of  mercury  (SO3HgO),  does  not  reach  the  lower  part  of 
the  zinc,  when  the  cell  is  placed,  as  shown  in  the  figure ; 
but  if  it  be  turned  upside  down  or  put  upon  its  side,  the 
liquid  comes  in  contact  with  the  electrodes  and  the  cur- 
rent begins  to  flow. 

The  cell  is  hermetically  closed,  and  there  is  no  danger 
of  any  leakage.  It  is  very  convenient  for  many  purposes, 
and  forms  part  of  some  Yolta-induction  apparatus  made 
by  Trouve. 

GAIFFE'S  BATTERY. 

Gaiffe  uses  the  sulphate  of  me'rcury  battery  for  his 
Yoltaic-induction  apparatus.  Two  cells  are  joined,  as 
Fig.  36  shows.  Each  cell  is  contained  in  a  small  sepa- 
rate vessel  of  ebonite,  at  the  bottom  of  which  is  a  carbon 


148  TWO-LIQUID   BATTERIES. 

plate.  Upon  the  carbon  is  placed  some  water  and  sul- 
phate of  protoxide  of  mercury.  A  small  plate  of  amal- 
gamated zinc  is  immersed  in  this  liquid,  and  is  furnished 
with  a  little  knob  in  the  centre  by  which  it  may  be  lifted 
out.  The  zinc  rests  upon  platinum  wires  fastened  in  the 


FIG.  36. 

moulding  of  the  ebonite,  which  establish  the  communica- 
tion with  the  carbon  of  the  adjoining  cell. 

These  batteries  may  work  for  about  an  hour,  when  the 
sulphate  should  be  removed.  This  liquid  is  generally 
freshly  made  every  time  the  induction  apparatus  is  used, 
and  the  old  water  and  yellow  sulphate  are  thrown  away. 

LATIMEK  CLARK'S  STANDARD   BATTERY. 

This  eminent  electrician  proposed  to  "  discover  a  form 
of  the  Yoltaic  battery  having  a  perfectly  constant  elec- 
tro-motive force  and  maintaining  an  invariable  difference 
of  potential  between  its  poles."  * 

He  has  found  that  the  voltaic  combination  which  best 
fills  these  conditions  is  an  element  composed  of  zinc,  sul- 
phate of  zinc,  sulphate  of  mercury,  and  mercury. 

The  zinc  ought  to  be  chemically  pure :  distilled  zinc  is 
used. 

The  formula  for  the  sulphate  of  mercury  is  Hg2OSO3 ; 
it  is  a  white  salt  that  does  not  become  yellow  by  the  ad- 


Philosophical  Transactions  of  the  Royal  Society,  June  19,  1875. 


BATTERIES   DEKIVED    FROM   THE  DANIELL.     149 

dition  of  water.  It  is  prepared  by  dissolving  pure  mer- 
cury in  warm  sulphuric  acid,  but  not  boiling ;  it  must  be 
carefully  washed,  because  the  presence  of  any  free  acid 
would  notably  change  the  results.  The  salt  must  con- 
tain no  sulphate  HgOSO3  (sulphate  of  protoxide),  recog- 
nized by  its  transformation  into  a  yellow  salt  by  the  action 
of  water. 

The  sulphate  of  zinc  should  be  pure  and  used  in  a 
state  of  saturation ;  it  can  be  easily  understood  that  its 
composition  can  thus  be  rendered  more  constant. 

The  battery  is  prepared  as  follows :  The  sulphate  of 
zinc  is  dissolved  in  distilled  boiling  water,  left  to  cool, 
gently  poured  off,  and  the  saturated  liquor  thus  obtained 
is  used  to  form  a  thick  paste  with  sulphate  of  mercury ; 
this  paste  is  heated  to  100°  centig.  in  order  to  expel  any 
air  it  may  contain.  It  is  then  poured  upon  the  previously 
heated  surface  of  the  mercury,  the  zinc  is  suspended  in 
the  paste,  and  finally  the  jar  is  closed  with  melted  paraffin. 

The  positive  connection  is  a  platinum  wire  passing 
through  a  glass  tube  and  descending  to  the  mercury.  A 
better  plan  is  to  place  this  positive  connection  in  an  out- 
side glass  tube  which  opens  into  the  jar  near  the  bottom. 

"  The  electro-motive  force  of  these  elements  is  remark- 
ably constant,  provided  they  remain  open  and  be  not 
weakened  by  work.  Numerous  experiments  have  been 
made  between  new  ones  and  others  which  had  been  used 
several  months,  and  it  was  found  that  the  greatest  dif- 
ferences did  not  reach  one  thousandth  part  of  the  total 
value  of  the  force." 

Experiments  have  been  made  to  determine  the  varia- 
tions in  the  electro-motive  force  with  the  temperature. 
The  average  showed  a  diminution  for  an  increase  of  tem- 
perature in  the  proportion  of  six  hundredth^  per  degree 


150  TWO-LIQUID   BATTERIES. 

centigrade.  The  variations  are  more  marked  as  the  ther- 
mometer nears  0°  centig.,  about  eight  hundredths  per  de- 
gree ;  from  5°  to  25°  they  are  about  .06  per  cent,  and 
about  .055  per  cent  up  to  100°  centig. 

Mr.  Clark  has  determined  the  electro-motive  force  in 
absolute  measurement,  and  has  found  it  to  be  1.4573 
volts,  and  1.4562  volts  with  a  sine  galvanometer,  the  tem- 
perature being  15.5°  centig. 

SULPHATE -OF -LEAD   BATTEKY. 

This  is  the  same  kind  of  battery  as  the  sulphate-of- 
mercury  battery.  It  is  a  Daniell  with  an  almost  insolu- 
ble depolarizing  salt ;  it  is  formed  of  zinc,  sulphate  of 
zinc,  sulphate  of  lead,  and  lead. 

The  cheapness  of  sulphate  of  lead  has  caused  this  bat- 
tery to  be  extensively  used,  but  it  has  finally  been  aban- 
doned for  certain  reasons,  which  we  will  give  farther  on. 

M.  Becquerel  was  the  first  to  try  this  combination. 
His  conducting  electrode  was  either  lead  or  a  piece  of 
carbon,  a  piece  of  copper  or  tin. 

In  1860  Marie  Davy  proposed  a  new  form  which  has 
been  abandoned  ;  it  deserves  notice,  however,  as  it  was  a 
good  imitation  of  Volta's  column  battery,  and  has  been 
imitated  in  turn  by  Sir  William  Thomson  in  his  large 
Daniell  gravity  battery. 

Marie  Davy's  elements  consisted  of  pans  of  tinned  iron 
provided  with  three  arms  placed  horizontally  and  at  equal 
distances  apart.  Upon  the  under  side  of  each  pan  was 
soldered  a  disc  of  zinc  covering  the  whole  bottom.  In 
each  pan  was  a  layer  of  sulphate  of  lead  about  -J  of  an 
inch  thick  and  a  portion  of  pure  water  or  water  con- 
taining a  little  sulphate  of  zinc.  The  pans  are  placed 


BATTERIES   DERIVED   FROM   THE  DANIELL.     151 

one  above  the  other,  so  that  the  zinc  of  one  is  immersed 
in  the  liquid  of  the  other  below  it.  It  is  necessary  to 
keep  the  successive  cells  at  equal  distances  apart,  which  is 
done  by  means  of  vertical  wooden  supports  to  which  the 
horizontal  arms  are  fastened.  A  battery  of  forty  cells  of 
this  kind  forms  a  column  about  40  inches  high.  This 
form,  however,  has  not  been  preserved ;  it  weakened 
rapidly,  and  we  believe  that  its  principal  defect  lay  in  the 
too  small  quantity  of  water  it  contained. 

M.  Edmond  Becquerel  gave  to  the  sulphate-of-lead 
battery  the  regular  form  of  porous  jar-cells.  He  ar- 
ranged a  solid  cylindrical  mass  of  sulphate  of  lead  around 
a  central  piece  of  lead  from  £  to  J  of  an  inch  in  diame- 
ter. Consistency  may  be  given  to  this  mass  by  mixing  it 
with  chloride  of  sodium  (100  grammes  of  dried  and 
crushed  sulphate  of  lead  and  20  grammes  of  sea-salt), 
and  by  wetting  it  with  a  saturated  solution  of  sea-salt  (50 
cubic  centimetres).  This  cylindrical  mass  of  sulphate  of 
lead  may  be  surrounded  by  a  layer  of  plaster,  which  serves 
as  a  porous  jar. 

Finally,  ordinary  porous  jars  may  be  used  containing 
the  lead  and  the  sulphate. 

One  of  the  faults  in  this  battery  is  that  its  electro- 
motive force  is  about  one  half  that  of  a  Daniell,  while  its 
resistance  is  very  great.  The  result  is  that,  in  order  to 
obtain  the  same  intensity,  a  number  of  cells  more  than 
double  that  of  the  Daniell  battery  is  required.  It  would 
seem,  from  the  foregoing,  that  this  battery  would  be 
badly  adapted  to  an  electric-bell  service,  as  the  bells  are 
placed  in  circuits  of  little  resistance,  and  their  electro- 
magnets themselves  have  but  little  resistance ;  therefore 
the  internal  resistance  of  the  battery  is  greater  than  that 
of  the  outside  circuit,  which  is  a  very  unfavorable  con- 


152  TWO-LIQUID   BATTERIES. 

dition.  It  is,  however,  to  this  use  that  the  battery  in 
question  has  been  put,  and  it  must  be  that  it  does  all  that 
is  required  of  it. 

It  would  seem  that  the  economy  resulting  from  the  use 
of  a  cheap  salt  would  be  more  than  balanced  by  the 
necessary  number  of  cells,  and  by  the  cost  of  so  much 
zinc  and  so  many  glass  and  porous  jars.  This  considera- 
tion must  have  finally  attracted  attention ;  for  sulphate- 
of-lead  batteries  have  been  gradually  abandoned. 

WEAKENING  OF  THE  SULPHATE  OF  LEAD 
BATTEEY. 

There  happens  in  the  battery  in  question  precisely 
what  we  have  seen  in  Marie  Davy's  batteiy :  the  sulphate 
of  lead  does  not  act  unless  dissolved.  This  dissolution  is 
slow,  and  if  the  consumption  of  electricity  is  active,  and 
consequently  that  of  the  dissolved  sulphate  of  lead,  the 
solution  weakens  and  the  battery  ceases  to  be  depolarized ; 
in  other  words,  the  battery  becomes  weakened. 

It  is  probable  that  if  an  energetic  current  were  made 
to  act  upon  the  battery  thus  polarized,  the  sulphate  of 
zinc  would  be  electrolyzed  and  zinc  would  be  deposited 
upon  the  lead,  as  in  Marie  Davy's  cell.  This  observation 
has  no  practical  interest,  but  only  tends  to  show  once 
more  the  great  similarity  of  the  sulphate-of-lead  battery 
to  the  mercurial-salt  battery. 

If  the  sulphate-of-lead  battery  were  again  to  be  used, 
we  believe  that  there  would  be  an  advantage  in  putting 
pieces  of  gas-retort  carbon  in  the  mass  of  sulphate  of  lead  ; 
this  would  facilitate  the  dissolving  of  that  salt  which  is 
the  condition  of  depolarization,  and  it  would  also  give  a 
greater  conductivity  to  the  mass  which  fills  the  porous  jar. 


BATTERIES   DERIVED   FROM   THE  DANIELL.     153 


VARIOUS  SALT  BATTERIES. 

By  substituting  for  the  sulphate  of  copper  and  zinc  in 
the  Daniell  the  corresponding  nitrates,  or  the  acetates, 
or  the  chlorides,  simple  modifications  of  the  Daniell  are 
obtained.  Kone  of  these  batteries  have  any  practical  in- 
terest, on  account  of  the  high  price  of  the  materials. 

M.  Jules  Regnauld  has  carefully  measured  the  electro- 
motive forces  of  several  of  these  batteries,  and  the  com- 
parison of  the  figures  is  worthy  of  attention. 

Pure  Zinc  Copper.  Electro-motive  force 

expressed  in  Volts. 

Sulphate  of  zinc Sulphate  of  copper 0.955 

Nitrate      "     "  Nitrate      "       "      0.873 

Acetate     "     "  Acetate     "       "      0.955 

Chloride    "     " Chloride  "       "      0.955 

The  equality  of  these  figures  is  very  interesting.  But 
from  these  particular  instances  no  law  of  physics  can  be 
deduced :  other  measurements  of  M.  Regnauld  show  that 
this  equality  does  not  exist  in  all  analogous  series  of  bat- 
teries. 


CHAPTER  V. 
ACID  BATTERIES. 

IN  the  beginning  of  Part  II.  of  this  work  we  indi- 
cated how  the  electrode  may  be  depolarized  by  means  of 
substances  rich  in  oxygen  and  easily  decomposed,  notably 
highly  oxygenated  acids.  The  experiment  which  we 
then  cited  is  due  to  Grove,  and  has  led  to  the  production 
of  one  of  the  best  batteries  known. 

GKOYE'S  BATTEKY. 

To  remain  faithful  to  our  method  of  exposition,  we 
should  consider  Grove's  battery  as  one  of  the  derivatives 
of  Yolta's.  In  the  latter  the  zinc  is  attacked  by  tlfe  di- 
lute suplmric  acid,  and  hydrogen  is  evolved  upon  the  con- 
ducting electrode,  copper,  platinum,  or  carbon.  If  this 
platinum  electrode  be  surrounded  by  nitric  acid,  the  latter 
is  decomposed,  oxygen  is  set  free  and  forms  water  with 
the  polarizing  hydrogen,  and  nitric  oxide  is  given  off. 
The  battery  thus  modified  is  without  polarization,  or,  in 
other  words,  is  constant.  It  is  known  by  the  name  of 
Grove's  battery,  and  dates  from  the  year  1839. 

That  which  is  commonly  called  Grove's  battery  con- 
tains a  conducting  electrode  of  platinum ;  it  is  under- 
stood, however,  that  Grove's  conception  is  a  general  one 
and  may  be  easily  modified.  Fig.  37  represents  this 
battery  under  its  most  common  form. 

A  square  porcelain  jar  is  used  as  the  outside  recipient ; 


ACID   BATTERIES.  155 

it  contains  a  well-amalgamated  zinc  electrode,  having  the 
shape  of  an  U.  Inside  of  the  zinc  thus  shaped  is  placed 
a  porous  jar  containing  a  very  thin  piece  of  platinum, 
which  serves  as  the  conducting  electrode ;  water  acidu- 
lated with  sulphuric  acid  is  put  with  the  zinc  in  the  out- 
side jar,  and  nitric  acid  fuming  is  poured  in  the  porous 
jar.  The  platinum  is  connected,  as  shown  in  the  figure, 
with  the  projecting  portion  of  the  zinc  in  the  adjoining 
cell. 

Such  is  the  form  of  Grove's  cell  employed  in  England 


FIG.  37. 

to  the  entire  exclusion  of  Bunsen's  form,  so  generally  used 
in  France.     "We  will  speak  of  the  latter  farther  on. 

In  Germany,  Poggendorfs  arrangement  of  Grove's 
cell  is  used.  The  porous  jar  is  cylindrical  and  contains 
the  platinum  in  the  shape  of  an  S,  in  order  to  offer  as 
large  a  surface  as  possible.  The  platinum  is  fastened  to 
a  porcelain  stopper  which  almost  completely  closes  the 
porous  jar.  This  arrangement  is  represented  by  Figs.  38 
and  38#.  We  will  not  dwell  any  longer  upon  it,  because 
we  believe  that  Grove's  battery  has  received  but  a  limited 


156 


TWO-LIQUID   BATTERIES. 


application  in  Germany,  and  that  Bunsen's  disposition  is 
generally  preferred. 

Our  main  object  is  more  to  make  known  those  batteries 
which,  in  one  country  or  another,  are  the  most  exten- 


sively  employed,  and  not  so  much  to  treat  of  the  many 
combinations  which  are  only  theoretically  interesting. 

CHEMICAL  ACTIONS  IN  GKOVE'S  BATTEEY. 

We  have  said  that  the  zinc  becomes  oxidized  at  the  ex- 
pense of  the  water  and  forms  sulphate  of  zinc ;  that  the 
hydrogen  of  the  water  thus  decomposed  reduces  nitric 
anhydride  (N2OB)  and  produces  nitric  oxide  (NO). 
This  latter  gas,  coming  in  contact  with  the  air,  is  trans- 
formed into  nitric  tetroxide,  recognizable  by  its  color  and 
by  its  suffocating  properties.  It  is  absolutely  certain  that 
the  Grove  batteries  produce  nitric  tetroxide ;  therefore 


ACID   BATTERIES.  157 

the  decomposition  of  nitric  acid  must  surely  produce  ni- 
tric oxide,  as  we  said  above  ;  but  that  this  is  the  only  form 
of  decomposition  that  takes  place  is  not  certain.  On  the 
contrary,  it  is  probable  that  nitric  trioxide  is  produced. 
This  appears  to  be  the  result  of  theoretical  considerations, 
into  the  details  of  which  we  cannot  enter.* 

Other  actions  take  place  in  Grove's  cell,  one  of  which 
is  the  formation  of  ammonia.  If,  in  fact,  after  the  liquids 
are  exhausted  they  be  evaporated,  it  is  observed  that  the 
addition  of  lime  in  the  concentrated  liquid  produces  an 
abundant  freeing  of  ammoniacal  gas.  This  proves  that  if 
a  portion  of  the  hydrogen  has  combined  with  the  oxygen 
of  the  nitric  acid  to  form  water,  another  portion  has  com- 
bined with  the  nitrogen  to  form  ammonia.f 

Unfortunately  batteries  have  not  been  completely  ex- 
amined from  a  chemical  point  of  view,  and  it  is  not 
known  precisely  what  takes  place  within  them.  To  com- 
pletely elucidate  the  question,  the  gases  evolved  in  each 
cell  should  be  separately  collected ;  then  these  gases  and 
also  the  matter  left  in  the  liquids  should  be  analyzed. 


PRACTICAL  DETAILS. 

The  platinum  electrodes  are  generally  5  in.  high  by 
2  in.  wide,  and  they  must  not  be  too  thin,  for  the  resist- 
ance would  thus  be  increased  in  a  manner  extremely  det- 
rimental to  the  desired  results. 

There  is  no  serious  disadvantage  in  permitting  the 
porous  jar  to  touch  the  zinc,  and  on  the  other  hand  it  is 
very  important  to  diminish  as  much  as  possible  the  dis- 

*  See  Daniell,  "  Introduction  to  Chemical  Philosophy." 
f  See  Gavarret,  "  Traite  d'Electricite,"  t.  ii.  p.  446. 


158  TWO-LIQUID   BATTERIES. 

tance  between  the  electrodes  and  consequently  the  resist- 
ance of  the  cells. 

The  U  form  of  the  zinc  is  riot  very  economical,  because 
it  breaks  at  the  bottom  before  it  is  worn  at  the  top.  It 
has  been  proposed  to  place  some  mercury  in  the  bottom 
of  the  porcelain  jar  and  to  use  two  zinc  plates,  one  on 
each  side  of  the  porous  jar,  which  are  thus  united  by  the 
mercury  at  the  bottom.  This  disposition,  which  we  have 
already  indicated  for  other  batteries,  allows  the  more  com- 
plete consumption  of  the  zinc. 

BTOSESPS  BATTEBY. 

In  the  beginning,  Grove  thought  of  substituting  char- 
coal or  even  gas-retort  carbon  for  the  platinum,  and  sev- 
eral public  experiments  were  made  in  London ;  these, 
however,  had  been  forgotten  when,  in  1843,  Bunsen  be- 
came possessed  of  the  same  idea  and  succeeded  in  intro- 
ducing the  general  use  of  his  arrangement. 

Without  further  insisting  upon  the  history  of  this  in- 
vention, we  will  first  describe  Bunsen's  battery  as  it  is 
used  in  France,  and  then  the  form  employed  in  Germany, 
which  is  very  like  that  originally  proposed  by  Bunsen. 

FKElSrCH  MODEL   (Fio.  39.) 

The  outside  jar  is  made  of  glazed  earthenware,  which 
is  less  fragile  than  glass,  and  this  consideration  is  impor- 
tant in  the  use  of  a  battery  which  is  often  moved  from 
one  place  to  another  at  greater  or  less  distances.  For  bat- 
teries which  always  remain  in  the  same  place  there  is  no 
inconvenience  in  the  use  of  glass  jars  ;  but  as  their  cost 
is  very  little  less  than  that  of  the  glazed  earthenware 


ACID    BATTERIES. 


159 


jars,  the  latter  are  nearly  always  used,  at  least  in  France. 
Earthenware  subject  to  fracture  should  be  avoided,  for 
the  acid  enters  into  the  cracks  of  the  enamel,  rendering 
the  jar  permeable  and  fragile. 

The  zinc  is  formed  of  a  plate  of  zinc  -£$  of  an  inch 
thick,  rolled  in  the  shape  of  a  cylinder  and  well  amalga- 
mated, which  latter  precaution  allows  the  zinc  to  be  left 


FIG.  39. 

twenty-four  hours  in  acidulated  water  without  its  being 
sensibly  dissolved. 

Some  persons  solder  to  the  zinc  a  strip  of  copper  which 
constitutes  the  negative  connection  of  the  cell ;  but  the 
two  must  be  riveted  together  by  means  of  a  copper  rivet, 
otherwise  the  mercury  will  finally  detach  one  from  the 
other.  These  means  of  connection  are,  however,  not  to 
be  recommended.  The  zinc  should  be  higher  than  the 


160  TWO-LIQUID   BATTEEIES. 

earthenware  jar  and  should  be  furnished  with  a  binding 
screw,  to  which  the  positive  connection  of  the  adjoining 
cell  is  attached.  This  arrangement  has  the  following  ad- 
vantages : 

1.  Every  time  the  battery  is  charged,  that  part  of  the 
binding  screw  which  comes  in  contact  with  the  zinc  (and 
that  part  alone)  should  be  cleaned   with  emery-paper. 
This  is  very  quickly  done,  and  assures  to  the  operator  a 
good  contact  at  those  points  through  which  the  current 
passes. 

2.  When,  after  having  used  the  battery  a  certain  num- 
ber of  times,  the  zinc  becomes  worn  at  the  bottom,  it  may 
be  turned  upside  down.     Thus  the  zinc  is  used  up  more 
completely  and  regularly  before  it  becomes  necessary  to 
renew  it. 

3.  The  zinc,  thus  reduced  to  a  simple  cylinder  having 
no  piece  of  any  kind  attached  to  it  is  easily  packed  and 
requires  but  a  small  box  for  transportation. 

The  porous  jar  is  placed  in  the  centre  of  the  zinc  cylin- 
der and  has  about  the  same  height.  It  should  be  very 
porous  and  permit  an  easy  communication  of  the  liquids 
it  separates. 

The  negative  electrode  has  the  shape  of  a  prism  with  a 
rectangular  base ;  it  should  reach  above  the  porous  jar, 
in  order  to  facilitate  the  connection.  "We  have  explained 
the  advantages  of  the  binding  screw,  and  we  here  repeat 
that  every  time  the  battery  is  recharged  the  parts  of  the 
binding  screw  which  touch  the  carbon  should  be  cleaned 
with  emery-paper,  in  order  to  secure  a  perfect  contact. 

Before  the  invention  of  the  binding  screws,  various 
more  or  less  imperfect  means  were  employed  for  the  con- 
nection with  the  carbon.  A  conical  copper  cork  was 
forced  into  a  hole  made  in  the  top  of  the  carbon  ;  or  cop- 


ACID    BATTERIES.  161 

per  was  deposited  upon  the  head  of  the  carbon,  to  which 
a  strip  of  copper  was  then  soldered.  Other  means,  some 
of  which  we  have  already  pointed  out,  were  also  em- 
ployed. 

All  of  them  presented  inconveniences  more  or  less 
marked,  and  we  do  not  hesitate  to  say  that  they  should 
all  be  discarded,  and  the  binding  screws  exclusively 
adopted.  These  latter  have  been  used  for  many  years  by 
those  persons  who  successfully  produce  electric  light  by 
means  of  batteries.  We  insist  upon  this  recommendation, 
because  a  single  imperfect  contact  suffices  to  cause  a  no- 
table loss  of  energy  in  a  battery  of  fifty  or  sixty  cells. 

AMALGAMATION  OF  THE  ZINC. 

We  have  said  above  that  it  is  necessary  to  amalgamate 
the  zinc.  If  this  precaution  be  neglected  when  the  zincs 
are  used  with  concentrated  acids,  gases  are  evolved  charged 
with  acid  vapors,  which  render  the  care  of  the  battery 
troublesome  arid  which  are  injurious  to  the  health. 

We  have  also  said  that  by  amalgamation  the  zinc  is 
made  more  electro-positive,  and  that  consequently  the 
electro-motive  force  of  the  cells  is  increased  (an  inspection 
of  the  tables  at  the  end  of  this  work  will  make  this  very 
plain). 

It  is  therefore  necessary  that  this  operation  be  made 
with  great  care,  and  the  simple  and  regular  form  of  the 
zinc  described  above  renders  the  process  comparatively 
easy. 

In  order  to  thoroughly  amalgamate  the  zinc,  it  should 
first  be  well  scraped  and  cleaned.  The  following  is  the 
process  which  we  recommend  : 

The   zincs  are  placed   on   end  in  a  bucket   of  water 


162  TWO-LIQUID   BATTERIES. 

containing  one  tenth  of  sulphuric  acid.  They  stand  out 
of  the  liquid  about  half  an  inch,  so  that  they  may  be  lifted 
out  without  immersing  one's  fingers  in  the  acid.  Three 
zincs  are  placed  at  one  time  in  the  bucket,  in  order  that 
each  one  may  remain  in  the  cleansing  solution  the  length 
of  time  required  for  the  amalgamation  of  the  other  two. 
A  rotation  is  established  in  the  following  manner :  Every 
time  that  one  zinc  is  taken  out  to  be  amalgamated  it  is 
replaced  by  a  new  one,  so  that  there  may  be  always  three 
in  the  cleansing  solution.  The  other  two  have  in  the 
mean  time  been  turned  upside  down,  in  order  to  immerse 
the  parts  which  were  exposed  to  the  air. 

The  vessel  containing  the  mercury  for  amalgamation 
has  the  shape  of  a  portion  of  a  cylinder ;  it  is  a  little 
longer  than  the  zincs  to  be  amalgamated.  This  is  the 
most  rational  form,  for  it  permits  the  use  of  the  smallest 
quantity  of  mercury.  The  zincs  are  carefully  immersed 
in  the  mercury,  the  longitudinal  opening  downwards,  in 
order  that  the  mercury  may  the  more  easily  reach  the  in- 
terior of  the  cylinder.  The  zincs  are  then  turned  slowly 
once  or  twice,  to  insure  the  amalgamation  of  the  entire 
surface.  At  the  moment  of  taking  the  zinc  out  of  the 
mercury  it  should  be  held  at  an  angle  of  ten  or  twelve 
degrees  to  allow  the  superfluous  mercury  to  run  off.  It 
is  then  lifted  out  in  a  horizontal  position  with  the  longi- 
tudinal opening  upwards,  so  that  no  drops  of  mercury 
may  run  off  at  the  angles  and  thus  be  lost. 

The  zincs  are  finally  placed  in  an  empty  tub  or  trough 
capable  of  containing  several  of  them  ;  after  a  certain  time 
a  quantity  of  mercury  is  found  at  the  bottom,  having  run 
off  from  each  zinc. 

The  vessel  used  for  amalgamation  is  of  enamelled  cast- 
iron,  thus  being  most  solid  and  unalterable. 


ACID   BATTEEIES.  163 

The  zincs  onglit  to  be  amalgamated  but  a  few  hours  be- 
fore the  battery  is  charged,  and  they  ought  to  be  re- 
amalgamated  every  time  the  battery  is  used,  even  if  there 
be  only  twelve  hours'  interval. 

The  cleaning  requires  a  little  longer  time  when  the 
zinc  is  new,  and  above  all  when  it  is  covered  with  layers 
of  adhering  salts  which  remain  from  preceding  operations. 

TO  MOUNT  THE  BATTERY. 

This  operation  requires  a  good  deal  of  method  for  a 
battery  of  fifty  or  sixty  cells,  such  as  is  used  for  electric- 
light  purposes. 

The  earthenware  jars  should  be  placed  at  short  distances 
from  each  other,  so  that  they  do  not  touch ;  they  should 
be  placed  in  one  row  or  in  two,  or,  if  room  permits,  in  a 
circle.  The  object  of  these  arrangements  is  to  facilitate 
the  filling  and  emptying  of  the  cells.  Place  the  cells,  if 
possible,  upon  a  table  covered  with  squares  of  porcelain  as 
are  frequently  found  in  laboratories,  or,  still  better,  upon 
rods  of  glass.  In  the  absence  of  the  above  conveniences, 
the  jars  may  be  ranged  upon  planks  of  dry  wood,  but  if 
possible  avoid  placing  them  upon  the  ground  in  the  open 
air.  It  can  be  easily  understood  that  there  is  an  advan- 
tage in  suppressing  all  losses  or  irregular  communications 
between  the  cells,  such  as  are  occasioned  if  the  jars  are 
damp,  or  if  they  are  placed  upon  damp  earth,  or  if  they 
touch  each  other.  A  striking  proof  of  the  existence  and 
importance  of  these  losses  is  shown  in  the  following  phe- 
nomenon, which  takes  place  every  time  the  above  precau- 
tions for  insulating  are  neglected  :  Whenever  one  touches 
any  one  of  the  poles  of  the  battery,  a  shock  is  felt  which 
is  caused  by  the  currents  passing  into  the  earth. 


164  TWO-LIQUID   BATTERIES. 

The  cause  of  these  communications  is  the  formation 
(upon  the  surfaces  of  the  jars  and  supports)  of  steam  and 
acid  vapors,  which  are  abundantly  freed  from  the  cells 
as  much  by  their  high  temperature  as  by  the  chemical 
action. 

As  soon  as  the  earthenware  jars  are  arranged,  the 
zincs,  the  porous  jars,  and  the  carbons  are  put  in,  the 
latter  being  first  furnished  with  their  respective  binding 
screws.  The  connections  are  then  made  between  the 
cells,  so  as  to  for.m  a  kind  of  chain,  commencing  with  the 
carbon  (positive  pole  of  the  battery)  and  ending  with  the 
zinc  (negative  pole  of  the  battery). 

Whether  the  cells  be  arranged  in  rows  or  in  a  circle, 
the  screws  and  connections  should  be  placed  so  as  to  be 
in  the  operator's  way  as  little  as  possible  when  he  is 
pouring  in  the  liquids. 

The  battery  may  be  thus  mounted,  without  any  incon- 
venience, several  hours  before  using  it,  since  it  contains 
no  liquids. 

TO  CHAKGE  THE  BATTEEY. 

If  the  porous  jars  are  new  there  is  an  advantage  in 
charging  the  cells  one  or  two  hours  before  using  the 
battery,  so  that  the  liquids  may  have  time  to  penetrate 
the  porous  jars. 

If,  on  the  other  hand,  the  porous  jars  have  already 
served,  they  have  retained  liquid  acids  in  their  pores,  and 
it  suffices  to  charge  the  battery  half  an  hour  or  even 
quarter  of  an  hour  before  working  it,  especially  if  the 
battery  is  to  work  more  than  three  or  four  hours. 

It  is  important  that  the  cells  be  charged  in  the  shortest 
time  possible,  in  order  that  those  first  charged  may  not 


ACID   BATTERIES.  165 

be  in  notably  different  conditions  from  the  last  ones ; 
therefore  preparations  should  be  made  in  advance,  and 
the  quickest  means  employed  for  pouring  in  the  liquids. 
Acidulated  water  should  be  prepared  in  a  large  tub,  in 
order  that  all  the  jars  may  contain  the  same  liquid. 
Thirty-three  jars  of  pure  water  (the  size  of  those  used  in 
the  battery)  and  three  jars  of  sulphuric  acid,  at  66° 
centigrade,  are  poured  into  the  tub.  The  water  is  put 
in  first,  and  then  the  sulphuric  acid  is  slowly  added, 
being  stirred  all  the  time,  in  order  to  render  the  mixture 
as  homogeneous  as  possible.  This  mixture  becomes 
greatly  heated,  as  is  known,  and  it'  the  temperature 
becomes  too  high  the  pouring  of  the  acid  should  be 
stopped,  and  the  liquid  in  the  tub  agitated  with  a  stick 
of  wood  or  a  rod  of  glass,  or  even  with  one  of  the  amal- 
gamated zincs  of  the  battery. 

This  mixture  can  very  well  be  prepared  several  hours 
in  advance ;  there  is  no  inconvenience  occasioned,  how- 
ever, in  using  it  before  it  cools  off — there  is  rather  an 
advantage.  The  only  important  point  is  that  it  be  per- 
fectly homogeneous,  or,  in  other  words,  well  mixed. 

The  liquid  is  generally  drawn  from  the  tub  in  a 
pitcher  and  poured  into  a  funnel  held  in  the  hand  over 
the  jars ;  this  is,  however,  very  fatiguing  for  the  operator, 
and  necessitates  strict  attention,  in  order  that  the  liquid 
may  be  at  the  same  level  in  all  the  jars.  We  recommend, 
therefore,  the  use  of  a  rubber  siphon,  like  that  used  in 
charging  the  Callaud  battery.  At  one  end  of  the  rubber 
tube  is  a  piece  of  glass  or  ebonite,  flattened  to  facilitate 
its  insertion  in  the  jars  between  the  zinc  and  porous  jar. 
At  the  other  end  there  is  an  ebonite  mouthpiece,  furnished 
with  lead,  in  order  that  it  may  descend  to  the  bottom  of 
the  reservoir  containing  the  liquids  used  to  fill  the  jars. 


166  TWO-LIQUID   BATTERIES. 

In  order  that  it  may  not  run  too  slowly,  the  reservoir 
should  be  placed  a  metre  higher  than  the  jars  to  be 
filled.  The  end  of  the  tube  is  held  in  the  hand,  and  it  is 
only  necessary  to  press  it  with  the  fingers  in  order  to  stop 
the  flowing.  This  system  dispenses  with  a  spigot,  produces 
an  instantaneous  stop,  and  allows  the  regulation,  within  a 
fraction  of  an  inch,  of  the  level  of  the  liquids  in  the  cells. 

The  liquid  is  started  in  the  siphon  in  the  following 
manner : 

In  the  hand  are  held  the  two  extremities  of  the  tube, 
which  hangs  below.  Water  is  poured  in  until  it  appears 
at  both  extremities,  then  the  mouthpiece  is  quickly  placed 
in  the  reservoir  of  acidulated  water  and  a  certain  quantity 
of  liquid  is  allowed  to  run  off,  in  order  to  purge  the  tube 
of  the  pure  water  it  contains.  From  that  time  on  every- 
thing is  ready  for  the  filling  of  the  jars. 

This  operation  terminated,  the  tube  should  be  well 
rinsed  with  water  containing  a  little  ammonia,  by  which 
precaution  it  may  be  made  to  serve  a  long  time. 

For  the  pouring  of  the  nitric  acid  a  funnel  or  bottle 
or  any  vessel  having  a  spout  may  be  used. 

The  siphon  may  also  be  used,  but  we  recommend 
"Wigner's  manner  of  starting  the  nitric  acid  in  the  siphon, 
which  is  done  as  follows : 

The  quantity  of  liquid  being  smaller,  it  may  be  put  in 
a  flask  whose  stopper  is  fitted  with  two  tubes,  one  going 
to  the  bottom  of  the  liquid  and  the  other  not  quite 
reaching  to  the  level  of  the  liquid.  By  blowing  in  this 
second  tube  the  liquid  is  forced  into  the  siphon,  by  means 
of  which  one  person  may  charge  fifty  or  sixty  cells  in 
twenty  or  twenty-five  minutes. 

A  very  neat  invention  of  Mr.  Lufbery,  for  the  emp- 
tying of  casks,  flasks,  etc.,  etc.  is  shown  in  Fig. 


ACID   BATTERIES. 


167 


The  special  stopper,  represented  apart  to  the  right  in  the 
cut,  is  conical  and  hollow,  and  can  be  adjusted  in  the 
mouth  of  any  bottle  or  flask.  This  stopper  is  fitted  with 
an  emptying  tube,  A,  and  a  tube,  B  ;  by  blowing  in  the 


FIG. 


latter  the  liquid  is  started  in  the  former.  The  spigot  at 
the  end  of  the  tube  A,  represented  to  the  left  in  the  cut, 
is  kept  closed  by  a  rubber  band.  It  is  opened  by  pressing 
the  upper  part  between  the  fingers. 


168  TWO-LIQUID  BATTEEIES. 

Analogous  arrangements  are  employed  in  all  labora- 
tories for  the  charging  of  batteries,  and  are  considered 
indispensable. 

TO  DISMOUNT  THE  BATTERY. 

It  is  plain  that  as  soon  as  the  battery  is  no  longer 
used,  there  is  an  advantage  in  stopping  the  waste  of  the 
zincs  and  the  acids,  which  is  done  by  taking  the  battery 
to  pieces. 

It  is  necessary  to  have  a  well-determined  method  for 
this  operation,  which  frequently  has  to  be  done  late  at 
night  and  with  a  very  poor  light.  Everything  must  be 
done  in  advance.  The  zincs  and  the  binding  screws  are 
placed  in  a  tub  of  clear  water ;  if  there  is  time  the  zincs 
may  be  taken  out  of  the  water  to  drip,  but  there  is  no 
disadvantage  in  allowing  them  to  pass  the  night  in  the 
water. 

The  carbons  must  then  be  taken  out  and  carefully 
ranged  in  special  earthenware  vessels.  It  is  better  not  to 
put  them  in  water  at  first,  but  to  allow  them  to  imbibe 
acids,  which  will  improve  them  for  the  future. 

The  contents  of  the  porous  jars  should  then  be  emptied, 
by  means  of  a  funnel,  into  the  vessel  destined  to  contain 
the  acid.  This  is  the  most  difficult  part  of  the  work 
because  of  the  very  abundant  vapors  given  off,  which 
occasion  a  violent  cough  if  proper  precautions  are  not 
taken  for  keeping  at  a  distance. 

It  is  almost  impossible  to  preserve  and  again  use  the 
water  acidulated  with  sulphuric  acid,  and  it  may  remain 
all  night  or  longer  in  the  jars  without  causing  any  incon- 
venience. 

The  nitric  acid  may  be  again  used  if  the  battery  has 


ACID   BATTERIES.  169 

not  worked  more  than  about  three  hours.  By  mixing  it 
with  some  fresh  acid,  it  may  be  used  in  the  same  battery 
and  for  the  same  length  of  time.  The  best  plan,  how- 
ever, is  to  sell  it  to  certain  branches  of  trade- where  old  as 
well  as  new  acids  may  be  employed. 

Finally,  the  acidulated  water  is  .thrown  out  and  the  jars 
completely  emptied ;  the  zincs  are  dried,  after  having 
been  left  a  certain  length  of  time  to  drip  ;  the  binding 
screws  are  dried  by  being  put  in  a  box  of  sawdust,  and 
finally  all  the  vessels  used  are  emptied  and  cleaned. 

Unless  one  has  been  in  the  habit  of  performing  this 
long  operation,  he  is  very  likely  to  burn  his  fingers  with 
the  acids ;  therefore  the  use  of  rubber  gloves  during  the 
work  is  recommended. 

It  is  a  good  plan  also  to  have  within  reach  a  little  am- 
monia, into  which  the  fingers  may  be  immersed  in  case 
of  any  accidents,  or  which  may  be  put  upon  any  spot  made 
on  the  clothes  by  the  acid. 

It  is  seen  that  the  use  of  a  large  Bunsen  or  Grove  bat- 
tery necessitates  a  long  and  tedious  piece  of  work,  espe- 
cially if  done  in  a  new  place  ;  the  work  is  much  less,  of 
course,  in  a  laboratory  where  one  has  everything  at  hand 
and  where  the  operation  has  been  performed  more  than 
once. 

If  the  battery  is  thus  taken  to  pieces  in  a  room,  there 
must  be  some  sort  of  an  arrangement  for  rapidly  carry- 
ing off  the  acid  vapors ;  otherwise  it  would  be  impossi- 
ble to  finish  the  work  or  even  to  enter  the  room. 

Some  employ  a  breathing  apparatus  like  that  of  M. 
Gallibert,  with  which  one  may  remain  in  a  place  filled 
with  a  dangerous  gas  without  any  inconvenience. 

In  order  that  the  zincs  may  be  well  preserved  during 
the  long  intervals  between  experiments,  they  should  be 


170  TWO-LIQUID   BATTERIES. 

carefully  dried  and  placed  on  end  one  above  another,  and 
only  coming  in  contact  at  several  points.  As  for  the 
porous  jars  and  the  carbons,  there  is,  as  we  have  said,  no 
advantage  in  rinsing  them  ;  it  is  indeed  better  to  allow 
them  to  imbibe  the  acids  of  the  battery,  which  gives  them 
a  more  immediate  conductivity  in  making  future  experi- 
ments. 

COMPOSITION  OF  THE  LIQUIDS. 

We  have  said  that,  in  general,  dilute  sulphuric  acid  is 
put  with  the  zinc  and  nitric  acid  with  the  carbon ;  but 
each  experimentalist  has  his  own  liquid,  and  some  of  these 
compositions  deserve  attention. 

We  have  stated  in  Part  I.,  that  a  solution  of  sulphu- 
ric acid  having  a  density  of  1.25,  and  composed  of  30 
parts  of  monohydrate  acid  for  70  parts  of  water,  pos- 
sessed the  greatest  conductivity,  and  that  it  is  never  used 
because  too  dangerous.  In  general,  liquids  containing 
eight  or  twelve  parts,  by  weight,  of  sulphuric  acid  for  a 
hundred  of  the  mixture  are  used,  whose  conductivity  dif- 
fers but  little  from  the  maximum.  In  the  practice, 
weights  being  more  difficult  to  establish  than  volumes, 
the  following  mixtures  are  used  :  one  volume  of  acid  for 
six  of  water,  or  three  volumes  of  acid  at  66  hydrometric 
degrees  for  thirty-three  of  water. 

The  electro-motive  force  decreases  (the  resistance  at 
the  same  time  increasing)  when  the  proportion  of  water  is 
increased  after  the  liquid  has  attained  the  density  1.25,  as 
is  shown  in  Table  VIII.  by  the  experiments  of  Paggendorf. 

Generally,  nitric  acid  at  40  hydrometric  degrees  is  em- 
ployed in  the  porous  jars ;  the  electro-motive  force  di- 
minishes notably  with  the  density  of  the  nitric  acid. 


ACID   BATTERIES.  171 

Some  persons,  and  especially  Wigner,  replace  the  nitric 
acid  by  a  mixture  of  two  parts  by  weight  of  nitric  acid 
(specific  gravity  1.360)  and  five  of  sulphuric  acid  (speci- 
fic gravity  1.845).  The  proportion  of  nitric  acid  is  some- 
times increased  to  three  and  a  half  parts,  if  the  battery  is 
to  work  more  than  four  or  five  hours. 

It  is  true  that  Wigner's  experiments  were  made  with 
the  Grove  battery,  which  is  only  employed  in  England, 


FIG.  40. 

but  it  appears  certain  that  the  same  results  might  be  ob- 
tained from  carbon  batteries. 

There  is  a  very  evident  economy  in  the  use  of  Wig- 
ner's  mixture,  as  sulphuric  acid  costs  much  less  than  nitric 
acid. 

In  1853  a  French  physicist  studied  this  question  and 
discovered  that  there  was  a  considerable  economy  in  sub- 
stituting for  the  nitric  acid  in  the  Bunsen  battery  a  con- 
centrated solution  of  sulphuric  acid  to  which  was  added 


172  TWO-LIQUID   BATTERIES. 

one  or  two  twentieths  of  nitric  acid.  Sulphuric  acid  evi- 
dently acts  as  an  absorbent  of  water,  and  renders  the  de- 
composition of  nitric  acid  much  more  effectual  than  when 
the  latter  is  in  a  large  quantity  of  water. 

As  sulphuric  acid  can  absorb  the  water  of  its  bulk  in 
nitric  acid,  which  is  successively  added  in  the  jar,  one 
may  almost  completely  use  up  a  given  quantity  of  nitric 
acid,  which,  if  used  alone,  would  have  to  be  thrown  away 
long  before  it  had  become  exhausted. 

GEKMAN  MODEL. 

In  the  beginning  Bunsen  placed  the  carbon  in  the  out- 
side jar  and  gave  it  the  form  of  a  hollow  cylinder,  in  the 
centre  of  which  was  placed  the  porous  jar.  The  porous 
jar  contained  the  amalgamated  zinc  with  acidulated  water. 


FIG.  41. 


This  form  has  been  preserved  in  Germany  and  abandoned 
in  France. 

Figs.  40,  41,  and  42  represent  the  Bunsen  cell  prop- 
erly so  called,  with  a  hollow  cylinder  of  rolled  zinc.      The 


ACID   BATTERIES.  173 

glass  jar  is  narrowed  at  the  top  in  order  to  check  the 
evaporation  of  the  nitric  acid. 

Sometimes  the  hollow  zinc  cylinder  is  replaced  by  a 
rod  of  cast  zinc.  Siemens  prefers  a  rod  of  cast  zinc 
whose  section  has  the  shape  of  a  cross. 

The  rod  of  zinc  inconveniently  reduces  the  space  occu- 
pied by  the  dilute  sulphuric  acid,  and  consequently  the 
quantity  of  the  acid.  The  other  two  dispositions  seem 


preferable.     Here  arises  the  question,  Which  is  the  better 
arrangement,  the  German  or  the  French  ? 

The  German  model  contains  more  nitric  acid,  which 
may  increase  and  prolong  the  constancy  of  the  battery. 
But  we  think  the  French  model  ought  to  be  preferred, 
because  in  the  German  arrangement  the  carbon  is  much 
more  expensive,  the  zinc  is  not  as  convenient  to  amalga- 
mate on  account  of  the  strip  and  ring  of  copper  soldered 
to  it,  and  the  expense  of  the  acid  is  greater. 


174  TWO-LIQUID   BATTERIES. 


FAUKE'S  MODEL. 

English  books  mention  a  form  of  carbon  battery  which 
deserves  notice.  The  carbon  proposed  by  Faure  has  the 
shape  of  a  bottle  closed  with  a  carbon  stopper.  This  car- 
bon serves  at  the  same  time  as  porous  jar  and  as  negative 
electrode.  It  contains  the  nitric  acid,  and  the  vapors 
which  free  themselves  force  the  liquid  into  the  pores  of 
the  carbon,  producing  depolarization. 

This  form  has  been  but  seldom  used.  It  would,  how- 
ever, be  worthy  of  study,  as  it  presents  economical  ad- 
vantages and  suppresses  nitric-acid  vapors,  which  render 
Bunsen's  cell  so  troublesome  and  indeed  dangerous  for 
the  men  who  have  the  care  of  a  large  number. 

ELECTEO-MOTIYE  FOECE  AND  EESISTANCE 
IN  NITEIC-ACID  BATTEEIES. 

All  physicists  agree  that  the  electro-motive  force  ot 
Bunsen's  battery  is  a  little  less  than  that  of  Grove :  the 
difference  is  very  small. 

As  to  that  of  Grove's  battery,  it  varies  from  '1.812  to 
1.512,  according  to  the  condition  of  the  acids. 

The  resistance  of  the  Bunsen  is  very  feeble,  and  if 
the  Daniell  be  taken  as  a  term  of  comparison,  it  is  found 
to  vary  from  4  to  10  ohms  ;  while  in  the  Grove  battery 
it  is  less  than  J  of  an  ohm,  at  least  in  the  beginning.  At 
the  expiration  of  several  hours  the  resistance  will  be 
found  to  have  greatly  increased  ;  but  if  the  liquids  have 
no  longer  the  same  composition,  the  battery  cannot  be 
considered  as  a  Grove.  We  have  often  said  that  the  re- 
sistance of  cells  is  so  variable  that  no  precise  information 


ACID   BATTERIES.  175 

can  be  given.  Only  a  general  idea  of  the  value  of  this 
resistance  for  each  kind  of  cell  may  be  given  ;  and  if  one 
desires  to  replace  Bunsen  cells  by  Daniell  cells,  it  is  easy 
to  obtain  the  same  electro-motive  force  by  doubling  the 
number  of  cells.  It  is  much  more  difficult,  however,  to 
obtain  as  feeble  a  resistance.  For  this  electrodes  having 
large  surfaces  must  be  employed,  and  they  must  also  be 
placed  very  near  each  other.  This  is  the  means  used  by 
Carre,  as  we  have  shown  in  Chapter  II.;  he  replaced  three 
of  Bunsen's  cells  by  five  of  DanielPs.  The  same  is  ob- 
tained with  Sir  William  Thomson's  battery. 

MAYXOOTH'S  BATTERY. 

Iron  may  be  substituted  for  the  carbon  in  Bunsen'g 
battery  without  sensibly  diminishing  the  electro-motive 
force.  The  battery  may  be  arranged  as  follows : 

In  a  cast-iron  pot  containing  nitro-sulphuric  acid — that 
is,  a  mixture  of  three  parts  by  weight  of  nitric  acid  and 
one  of  sulphuric  acid — is  placed  the  porous  jar,  which 
contains  the  amalgamated  zinc  and  water  with  one  tenth 
sulphuric  acid.  The  iron  pot  serves  at  the  same  time  as 
negative  or  conducting  electrode  and  outside  jar  of  the 
battery.  The  advantages  of  this  arrangement  are  very 
evident.  Those  who  employed  this  battery  appear  to 
have  been  well  satisfied  with  it,  and  we  cannot  imagine 
why  it  is  so  little  used. 

The  part  which  iron  takes  in  this  arrangement  has 
given  rise  to  many  interesting  researches.  It  is  said  that 
the  iron  is  rendered  passive  by  its  contact  with  the  almost 
saturated  solution  of  nitric  acid. 


176  TWO-LIQUID   BATTERIES. 


DAOTELL'S  EXPEKIMEOTS   UPON  THE    SIZE 
AND  PLACE  OF  THE  ELECTKODES. 

We  have  explained,  in  speaking  of  single-liquid  bat- 
teries, the  advantage  of  giving  a  much  larger  surface  to 
the  negative  electrode  than  to  the  positive.  Those  rea- 
sons do  not  apply  to  completely  depolarized  batteries,  such 
as  those  of  Daniell  and  Grove.  It  may  be  said  that  the 
surface  of  either  electrode  can  be  indifferently  increased 
or  reduced  ;  we  mean  that  the  reasons  which  should  lead 
to  the  arrangement  of  the  battery  are  simply  those  per- 
taining to  economy  and  practical  convenience,  and  that 
the  electro-motive  force  is  the  same  in  both  instances. 

Daniell  has  made  some  very  conclusive  experiments 
with  regard  to  this  subject.  He  constructed  two  Grove 
cells  of  identical  dimensions.  In  one  the  soluble  elec- 
trode was  in  the  shape  of  a  large  zinc  wire,  and  the  plati- 
num had  the  form  of  a  cylinder  and  surrounded  the 
cylindrical  porous  jar.  In  the  other,  the  forms  remain- 
ing the  same,  the  platinum  was  placed  in  the  centre  and 
the  zinc  outside.  The  intensity  when  measured  was 
found  to  be  essentially  the  same. 

Daniell  repeated  this  experiment  in  diminishing  the  di- 
ameter of  the  outside  cylinder  without  changing  its  height, 
and  found  the  same  intensity  as  in  the  first  instance. 
"Whence  the  very  curious  conclusion  that  the  internal 
resistance  of  the  cell  does  not  alter  when  the  diameter  of 
the  zinc  cylinder  alone  is  changed,  all  the  parts  of  the  cell 
being  concentrically  disposed,  and  the  central  electrode 
reduced  to  the  size  of  a  wire.  The  simple  reason  of  this, 
which  may  at  first  appear  strange,  is  that  if  the  distance 


ACID   BATTEKIES.  177 

of  the   electrodes  increases,  the  average  section  of  the 
liquid  increases  in  exactly  the  same  proportion. 

A  close  examination  will  show  that  this  rule  ceases  to 
be  true  when  the  central  electrode  is  of  a  certain  size ; 
in  this  case  there  is  always  an  advantage  in  diminishing 
the  distance  between  the  electrodes  and  in  increasing  the 
dimensions  of  the  electrode  in  the  porous  jar. 

CHLORIC -ACID   BATTERY. 

In  a  series  of  very  varied  experiments  a  chloric-acid 
battery  was  tried.  This  acid,  when  dissolved,  furnishes 
relatively  active  results,  which  increase  in  energy  as  the 
solution  approaches  saturation. 

Although  this  battery  can  never  be  employed  in  the 
practice,  we  mention  it  in  order  to  show  that  cells  can 
be  made  after  the  model  of  those  of  Grove  or  of  Bun- 
sen. 

CHROMIC -ACID  BATTERY. 

The  battery  in  which  the  depolarizing  agent  is  a  mix- 
ture of  bichromate  of  potass  and  sulphuric  acid  is  some- 
times designated  by  the  above  name.  If  free  chromic- 
ium  acid  has  ever  been  employed,  it  has  only  been  in 
scientific  experiments ;  it  is  impossible  to  make  use  of 
it  in  practical  applications. 

VARIOUS  ACID  BATTERIES. 

It  has  been  proved  that  hydrochloric  acid  has  no  de- 
polarizing property,  since  hydrogen  has  no  effect  upon 
this  acid. 


178  TWO-LIQUID   BATTERIES. 

Upon  the  other  hand,  it  has  been  established  that  a 
mixture  of  nitric  and  hydrochloric  acids  has  a  very 
marked  action,  which  is  easily  understood,  as  this  mixture 
is  a  very  energetic  oxidant  and  very  readily  absorbs  the 
hydrogen. 


OHAPTEE  VI. 
OXIDES  IN  BATTERIES. 

WE  have  seen  that  oxygenated  acids  cause  the  depolar- 
ization of  the  conducting  electrode  with  which  it  is  placed 
by  being  decomposed  and  oxidizing  the  hydrogen  to  form 
water. 

Analogous  results  may  be  obtained  by  using  oxides, 
such  as  the  peroxide  of  lead  and  the  bioxide  of  man- 
ganese. 

Every  oxide  easily  decomposed — the  bioxide  of  hydro- 
gen, the  bioxide  of  silver,  the  oxide  of  mercury — would 
give  much  energy  to  the  batteries  in  which  they  are  used, 
but  the  instability  of  the  bioxide  of  hydrogen,  as  well  as 
the  cost  of  the  others,  does  not  permit  the  use  of  these 
substances  in  the  practice. 

PEEOXIDE-OF-LEAD  BATTEET. 

About  thirty  years  ago  De  La  Eive  constructed  a  bat- 
tery in  which  depolarization  was  effected  by  means  of 
peroxide  of  lead.  He  put  the  peroxide  in  a  porous  jar 
containing  a  plate  of  platinum,  and  thus  obtained  a  bat- 
tery whose  electro-motive  force  was  superior  to  that  of  the 
Bunsen.  We  believe  that  a  plate  of  lead  or  of  carbon 
would  have  done  just  as  well,  and  would  certainly  have 
cost  less. 

Unfortunately,  we  do  not  know  whether  the  depolari- 
zation was  complete  or  not.  We  believe  that  by 


180  TWO-LIQUID   BATTERIES. 

employing  ordinary  minium  and  by  mixing  it  with 
pieces  of  crushed  '  carbon,  as  we  have  several  times 
recommended  in.  the  foregoing,  a  very  economical  and 
satisfactory  battery  might  be  obtained. 

It  must  be  noted,  however,  that  if  at  the  same  time 
sulphuric  acid  is  used  with  the  zinc,  there  will  be  a 
formation  of  sulphate  of  lead,  which,  on  account  of  its 
insolubility,  might  check  further  action.  It  will  be 
remembered  that  the  advantages  of  the  Daniell  battery 
consist  in  the  great  solubility  of  the  salt  formed  (sulphate 
of  zinc).  Whatever  may  be  done,  and  from  whatever 
stand-point  batteries  may  be  regarded,  one  is  always  led 
to  the  choice  of  DanielPs  sulphate-of -copper  battery  as  a 
model. 

PEROXIDE-  OF  -MANGANESE  BATTEEY. 

At  the  same  period  De  La  Rive  made  another  battery, 
analogous  to  the  preceding  one,  by  substituting  peroxide 
of  manganese  for  peroxide  of  lead.  He  found,  however, 
that  this  battery  wras  inferior  to  the  preceding  one. 

It  is  certain,  in  effect,  that  the  manganese  battery 
ought  to  have  a  much  smaller  electro-motive  force  than 
the  peroxide-of-lead  battery,  and  that  the  depolarization 
ought  to  be  very  imperfect.  Whatever  may  have  been 
the  reasons,  this  battery  wras  completely  forgotten  when 
Leclanche  commenced  his  researches,  which  resulted  in 
the  production  of  one  of  the  most  extensively  used  and 
best  batteries,  for  certain  instances,  ever  invented. 

LECLANCHE'S  BATTEEY. 

A  cell  of  this  battery  is  shown  in  Fig.  43.  The 
outside  glass  jar  is  square,  which  allows  the  placing  of  a 


OXIDES   IN   BATTERIES. 


181 


large  number  in  a  comparatively  small  box,  thus  render- 
ing the  battery  less  cumbersome.  The  glass  jar  is 
narrowed  at  the  top,  just  leaving  room  for  the  cylindrical 
porous  jar  to  be  put  in  or  taken  out,  which  almost  closes 
the  glass  jar,  thus  diminishing  any  possible  evaporation 


FIG.  43. 

of  the  liquid.  The  narrow  part  of  the  jar  is  furnished 
with  an  orifice,  through  which  the  zinc  is  passed,  and 
which  is  also  convenient  in  pouring  out  the  liquid 
contained  in  the  jar. 

The  soluble  electrode  is  formed  of  a  simple  cylindrical 


182  TWO-LIQUID   BATTERIES. 

piece  of  zinc,  about  half  an  inch  in  diameter.  A  little 
hole  is  made  in  the  centre  of  the  top  of  the  zinc,  in  which 
a  galvanized  iron  wire  is  soldered.  This  connection  is  at 
the  same  time  flexible  and  solid  ;  it  may  be  wound  in  the 
shape  of  a  helix,  which  gives  it  an  elasticity  frequently 
very  convenient. 

The  porous  jar  has,  as  we  have  said,  about  the  same 
diameter  as  the  mouth  of  the  glass  jar,  and  contains  almost 
equal  parts  of  peroxide  of  manganese  and  crushed  carbon. 
In  the  centre  of  this  mass  is  a  bar  of  carbon,  capped  with 
lead,  to  which  the  positive  binding  screw  is  attached. 

The  outside  jar  is  about  half  filled  with  water  and 
ammonia-hydrochlorate.  After  a  short  time  the  liquid 
penetrates  the  porous  jar  and  enters  into  the  mass  it 
contains. 

The  mixture  of  peroxide  and  carbon  is  covered  with 
wax,  to  prevent  its  spilling  during  transportation.  There 
is  a  hole  in  this  covering  to  allow  the  air  to  escape  when 
the  water  penetrates  the  porous  jar. 

ADVANTAGES  OF  LECLASTCHfi'S  BATTEEY. 

This  battery  .presents  many  advantages,  which  we  will 
enumerate : 

1.  The  zinc  is  not  attacked  by  the  sal  ammoniac. 
There  is  no  chemical  action  in  the  battery  while  the 
circuit  is  open,  or,  in  other  words,  there  is  no  waste  of 
material  as  long  as  there  is  no  outside  current  produced. 
We  have  already  spoken  in  detail  upon  this  point  in  the 
description  of  sal-ammoniac  batteries  (single  liquid)  ;  and 
we  would  only  say  that,  from  a  practical  point  of  view, 
this  peculiarity  constitutes  an  incontestable  superiority  of 
the  Leclanche  battery  over  that  of  Daniell. 


OXIDES   IN   BATTEEIES.  183 

2.  On    account    of    the   depolarizing   action  of     the 
peroxide  of  manganese,  the  electro-motive  force  at  first 
starting  of  this  cell  is,  as  given  by  Leclanche  himself.  1.38 
(DdnielPs  cell  taken  as  unit).     It  has  indeed  always  been 
possible  to  replace,  in  the  telegraph  and  analogous  appli- 
cations, a  certain  number  of  DanielPs  cells  by  a  smaller 
number  of  peroxide-of -manganese  cells.    Leclanche  states 
that  twenty-four  of  his  cells  can  replace  forty  of  Dan- 
iell's. 

3.  This    battery  has  but  a  comparatively  feeble    re- 
sistance, resulting  from  the  conductivity  of  the  peroxide 
of  manganese   and   of  the   carbon,  and  also  from  the 
considerable  mass  of  the  conducting  electrode.     In  the 
model,   in   which   the  porous   jars   are  5£  in.  high,  the 
resistance  is  between  5J  and  6  units. 

With  equal  dimensions  the  Leclanche  has  less  resistance 
than  the  Daniell,  which  constitutes  still  another  superi- 
ority. 

It  is  evident  that  if  the  zinc,  instead  of  being  a  rod 
half  an  inch  in  diameter,  were  rolled  in  the  form  of  a  cyl- 
inder surrounding  the  porous  jar,  as  in  the  usual  disposi- 
tion of  batteries,  the  resistance  of  the  cell  would  be  still 
less.  As  there  is  no  consumption  of  zinc  while  the  circuit 
is  open,  there  is  no  inconvenience  in  increasing  its  surface. 
Consequently  there  is  a  means  of  reducing  the  resistance 
of  a  Leclanche  cell,  if  in  any  particular  instance  it  might 
be  of  advantage. 

We  will  give,  further  on,  the  reasons  which  determined 
Leclanche  in  the  choice  of  the  dimensions  given  to  the 
soluble  electrode. 

4.  The    battery  contains    no     poisonous    substances, 
neither  does  it   throw  off  any  acid  vapors  nor  any  ap- 
preciable odor. 


184  TWO-LIQUID   BATTERIES. 

5.  The    first    cost  of    the  materials  is  comparatively 
small. 

6.  The  battery  resists  intense  cold  without  freezing, 
and   consequently  without    ceasing   to  work,  which    is 
proved  by  the  following  experiment : 

A  freezing  mixture,  at  —  25°  C.,  was  placed  around  a 
Leclanche  cell,  in  which  the  thermometer  finally  de- 
scended to  —  16°  C.,  without  causing  any  appreciable 
slackening  in  the  movement  of  an  electric  bell  upon 
which  the  cell  worked.  The  cell  was  shaken  or  left 
perfectly  still,  and  in  neither  instance  was  any  weakening 
(with  this  summary  means  of  comparison)  or  tendency  to 
freeze  observed. 

This  battery  presents,  in  this  respect,  still  another 
notable  advantage  over  the  Daniell,  which  freezes  in 
France  during  severe  winters.  The  direct  experiment 
shows  that  a  saturated  solution  of  sulphate  of  copper 
freezes  at  — 5°  C.,  and  a  concentrated  solution  of  sulphate 
of  zinc  at  —7°  C. 

A  recent  publication  of  Leclanche  states  that  the  re- 
sistance of  his  cell  varies  from  2.33  units  at  -|-  10°  C.  to 
4.22  units  at— 18°  C.,  whereas  that  of  the  Daniell  increases 
from  8.35  at  +10°  C.  to  12.58  at  0°  C.,  and  to  14.00  at 
—4°  C.  If  the  temperature  continues  to  lower,  at— 6°  C. 
the  liquids  become  pasty,  and  towards  —  20°  C.  the  re- 
sistance reaches  200  units. 

All  this  goes  to  show  that  the  Leclanche  battery  never 
freezes,  and  that  it  should  be  used  in  preference  to  all 
others  in  all  northern  countries. 

These  advantages  are  of  great  practical  importance,  and 
explain  the  success  of  this  battery,  which  is  to-day  the 
most  extensively  used  for  telegraphs,  electric  bells,  and 
other  analogous  applications  of  electricity. 


OXIDES   IN  BATTERIES.  185 

Any  number  of  these  cells  may  be  prepared  in  ad- 
vance and  stored  away  without  putting  the  liquid  in  them, 
ready  for  use  at  any  moment. 

After  having  been  charged,  they  may  be  left  a  long 
time  without  much  evaporation  of  the  liquid  and  without 
any  consumption  of  the  materials.  Their  form  facilitates 
transportation,  and  is  capable  of  being  modified,  as  will 
be  seen,  in  order  to  obtain  a  perfectly  closed  battery.  No 
care  is  needed  for  months  at  a  time  ;  it  depends,  of  course, 
upon  the  activity  of  the  work  to  be  done. 

The  cell  furnishes  a  more  intense  current  than  a  Dan- 
iell  of  the  same  size,  and  almost  as  intense  as  one  of  Marie 
Davy's  cells. 

One  must  be  careful,  however,  not  to  use  this  battery 
for  purposes  to  which  it  is  not  fitted  :  for  instance,  when 
a  continuous  current  or  a  great  quantity  of  electricity  is 
desired. 

CONSTRUCTION  AND  USE. 

1.  We  have  had  occasion  to  speak  of  the  advantage  of 
rolled  zinc  over  cast  zinc ;  we  add  that  drawn  zinc  is  bet- 
ter than  either,  as  it  is  more  dense  and  the  pores  are  less 
open.  Little  scales  are  sometimes  seen  to  detach  them- 
selves from  the  rolled  zinc,  which  denotes  some  irregular 
action  of  the  liquids  upon  the  metal.  There  is  nothing 
of  the  kind  apparent  with  the  drawn  zinc,  undoubtedly 
because  it  is  more  homogeneous. 

We  have  fully  explained  why,  in  single-liquid  batteries, 
there  is  an  advantage  in  giving  a  greater  surface  to  the 
conducting  electrode  than  to  the  soluble  electrode.  The 
same  reasons  hold  good  for  imperfectly  depolarized  bat- 
teries, such  as  that  of  Leclanche  ;  it  is  seen  how  the  in- 
ventor reduced  the  zinc  to  a  small  rod.  We  will  again 


186  TWO-LIQUID   BATTERIES. 

have  occasion  to  speak  of  the  dimensions  of  the  electrode, 
which  is  quite  a  delicate  and  important  question. 

2.  Leclanche,  in  recommending  amalgamation  of  the 
zinc,  says : 

"  In  this  battery,  where  there  is  no  acid,  the  zinc  should 
be  used  according  to  the  theory,  without  amalgamation. 
But  while  the  battery  is  at  work  the  attack  upon  the  zinc 
roughens  its  surface,  thus  facilitating  the  adherence  of 
saline  crystallizations  when  the  temperature  varies ; 
whereas  amalgamated  zinc  always  presents  a  surface  free 
from  crystals,  which  fall  to  the  bottom  of  the  jar  and  do 
not  diminish  the  conducting  surface  of  zinc." 

3.  It  is  very  important  to  employ  sal  ammoniac  as  pure 
as  possible.     That  purified  by  sublimation  is  the  best,  al- 
though a  little  costly.     Very  good,  however,  can  be  found 
which  has  not  undergone  this  process  of  purification. 
Care  should  be  taken  that  the  sal  ammoniac  be  not  dis- 
solved in  vessels  of  lead,  for  it  would  then  contain  several 
parts  of  chloride  or  of  sulphate  of  lead.     This  condition 
would  cause  the  loss  of  the  principal  advantage  of  the 
battery  ;  for  a  local  cell  (zinc-lead)  would  soon  form  which 
would  produce  a  constant  and  rapid  waste  of  the  zinc  and 
sal  ammoniac. 

4.  It  is  best  to  use  an  almost  saturated  solution  ;  there 
is,  indeed,  no  inconvenience  in  putting  a  little  more  salt 
than  is  necessary  in  the  jar ;  it  will  dissolve  in  proportion 
as  it  is  consumed  by  the  action  of  the  battery. 

By  the  action  of  the  battery  salts  are  formed,  and 
notably  oxychloride  of  zinc,  which  is  more  easily  dis- 
solved in  a  saturated  solution  than  in  a  weaker  one ;  there 
is  therefore  an  advantage  in  using  a  saturated  solution, 
and  it  should  not  be  allowed  to  weaken.  In  effect,  it  can 
be  understood  that  if  oxychloride-of-zinc  crystals  attach 


OXIDES   IN   BATTERIES.  187 

themselves  to  the  zinc,  its  active  surface  is  reduced  and 
the  resistance  of  the  battery  increased ;  the  intensity  of 
the  battery  might  thus  be  greatly  diminished.  If,  how- 
ever, too  large  a  quantity  of  sal  ammoniac  be  added  there 
will  be  the  same  result.  This  salt  crystallizes  upon  the 
surface  of  the  zinc,  and  the  resistance  of  the  battery  be- 
comes considerable.  There  can  be  no  doubt  as  to  the 
truth  of  this  way  of  explaining  things ;  for  if  the  zincs  be 
cleaned,  the  resistance  will  be  diminished  and  the  inten- 
sity brought  back  to  its  normal  value.  This  observation 
is  of  great  practical  importance,  because  employes  of  little 
instruction  are  very  apt  to  attribute  to  the  battery  all  the 
faults  that  arise  in  telegraph  offices,  without  being  able  to 
distinguish  the  cause ;  they  believe  the  battery  to  be 
weakened,  and  think  to  restore  its  energy  by  adding  more 
sal  ammoniac  ;  they  create,  in  reality,  the  fault  which  they 
intend  to  correct. 

5.  The  quality  of   the  bioxide  of  manganese  is  also 
very  important :  that  which  gives  the  best  results  is  the 
needle  manganese ;  it  is  crystallized,  silky,  and  presents  a 
graphite  appearance ;  if,  in  addition  to  these  properties,  it 
is  hard,  it  possesses  very  great  conductivity.     To  use  it, 
all  foreign  materials  must  first  be  taken  off ;  then  it  is 
crushed,  and  finally  sifted  to  get  rid  of  the  powder.     An 
equal  volume  of  crushed  carbon   is  then  added.     The 
mixture  thus  obtained  is  a  very  good  conductor  of  elec- 
tricity. 

6.  It  is  very  important  not  to  use  powdered  bioxide  of 
manganese.     The   results  of  experiments  by  Leclanche 
show  that  polarization  would  be  five  times  greater  in  a 
cell  containing  fine  powder  than  in  a  cell  constructed  af- 
ter the  manner  indicated  above,  with  grains  of  a  certain 
size. 


188  TWO-LIQUID   BATTEKIES. 

The  resistance  of  the  fine  powder  reaches  150  or  200 
units;  it  is  considerably  greater  than  that  of  the  liquid 
with  which  it  is  dampened ;  consequently  the  hydrogen, 
instead  of  distributing  itself  throughout  the  whole  mass, 
goes  straight  to  the  carbon  plate  and  is  not  absorbed.  On 
the  other  hand,  the  resistance  of  the  coarser  powder,  as 
recommended  above,  is  from  12  to  15  units  inferior  to 
that  of  the  liquid  of  the  battery,  and  consequently  the 
hydrogen  is  distributed  and  absorbed  in  the  whole 
mass. 

7.  The  porous  jar  should  only  be  half  filled  with  the 
liquid.     The  inventor  says  that  the  dryer  the  matter  con- 
tained in  the  porous  jar  the  better  the  conditions  of  con 
ductivity  and  working. 

It  wrill  be  seen  as  we  advance  that,  by  following  this 
order  of  ideas,  he  has  greatly  improved  his  battery. 

8.  There  is  an  advantage  in  using  very   porous  dia- 
phragms, in  order  that  the  action  may  begin  as  soon  as 
the  liquid  has  been  poured  in. 

The  quality  of  the  porous  jars  is  also  very  important. 
It  appears  that  those  of  Wedgwood,  though  excellent  for 
other  batteries,  are  not  worth  anything  in  the  Leclanche, 
The  English  have  had  a  good  deal  of  trouble  with  porous 
jars  wrhich  chip  oft  or  burst  by  the  solidification  of  the 
double  salts  of  zinc  and  ammonium.  Neither  in  France 
nor  in  Germany  has  any  inconvenience  of  this  kind  arisen. 

KEVEESED  FORM   OF  LECL'ANCIlfi'S 
BATTERY. 

In  this  form  the  zinc  is  placed  in  the  central  porous 
jar  and  surrounded  by  the  mixture  of  peroxide  of  man- 
ganese and  carbon.  This  disposition  necessitates  a  large 


OXIDES   IN   BATTERIES.  189 

quantity  of  manganese  as  compared  with  the  sal  ammo- 
niac, and  it  is  that  which  led  to  its  being  tried.  There  is 
no  doubt  as  to  the  slow  polarization  of  the  battery  thus 
arranged. 

The  volume  of  liquid,  however,  is  much  smaller  than 
in  the  original  form,  which  presents  a  grave  inconve- 
nience ;  because  the  liquid  has  thus  to  be  renewed  very 
frequently,  and  the  battery  loses  many  of  its  advantages. 
In  the  ordinary  battery  there  is  a  quantity  of  manganese 
corresponding  to  the  use  of  two  zinc  plates  and  to  two 
charges  of  sal  ammoniac.  In  the  reversed  form  there  is 
enough  for  the  use  of  six  or  eight  zinc  plates  and  for 
twenty  charges  of  sal  ammoniac :  it  is  a  marked  dispro- 
portion. 

For  these  reasons  the  reversed  form  has  obtained  but 
little  success,  and  should  be  only  employed  in  especial  in- 
stances. 

AGGLOMERATED  -  MIXTURE  BATTERY. 

As  the  liquid  has  less  conductivity  than  the  bioxide  of 
manganese  mixed  with  carbon,  it  is  easily  understood  that 
the  resistance  of  the  element  will  be  diminished  if  the 

0 

carbon  electrode  is  well  surrounded  by  the  mixture  in 
question,  rather  than  by  the  liquid. 

Leclanche  observed  that  the  conductivity  increased  as 
the  matter  contained  in  the  porous  jar  became  more  com- 
pact ;  that  is,  as  the  empty  spaces  filled  by  the  liquid  be- 
came less. 

In  following  up  this  idea  he  was  led  to  increase  the 
compactness  to  its  maximum,  by  compressing  the  mixture 
with  a  hydraulic  press.  Porous  jars  became  inconve- 
nient ;  he  suppressed  them  and  added  to  the  mixture  a 


190 


TWO-LIQUID   BATTEKIES. 


cement  which  held  the  mass  together,  thus  constituting 
an  agglomerate  in  which  the  carbon  was  tightly  held 
which  served  as  the  conducting  electrode. 

The  mixture  is  composed  of  40  parts  of  bioxide  of 
manganese,  55  of  carbon,  and  5  of  gum  lac,  which  serves 
to  agglomerate  the  whole  together  (Fig.  44). 

Finally,  the  inventor  added  in  the  interior  of  the  ag- 
glomerate 3  or  4  per  cent,  of  bisulphate  of  potash,  which 

facilitates  the  dissolution  of  the 
oxy chloride  which,  in  the  long- 
run,  enters  into  the  pores  of  tlu 
mixture. 

The  porous  jar  being  sup- 
pressed, some  particular  disposi- 
tion must  be  adopted  to  prevent 
the  zinc  from  touching  the  ag- 
glomerate, for  if  there  were  con- 
tact between  them  there  would 
be  the  formation  of  a  local  cell 
and  lost  work.  Between  the  zinc  and  agglomerate  a  small 
strip  of  wood  might  be  placed  and  the  whole  be  held  to- 
gether by  two  rubber  bands.  The  zinc  may  also  be  put  in 
a  small  glazed  or  unglazed  earthenware  jar  whose  walls 
are  pierced  with  holes,  which  prevents  the  contact  be- 
tween the  electrodes  and  at  the  same  time  permits  a  free 
circulation  of  the  liquid  in  the  outer  jar.  Two  projecting 
rubber  bands  may  be  placed  around  the  zinc,  which  pre- 
vent the  contact  between  the  zinc  and  the  agglomerate. 

The  agglomerate,  once  exhausted  by  long  work  of  the 
battery,  is  not  worth  anything ;  the  zinc  which  caps  the 
carbon  may  be  easily  taken  off,  as  also  the  binding  screw 
to  which  the  negative  connection  of  the  adjoining  cell  is 
attached.  The  mass  of  carbon  and  of  sesqui oxide  of  man- 


FIG.  44. 


OXIDES   IN  BATTERIES.  191 

ganese  may  be  thrown  away  and  the  zinc  and  brass  sold 
for  old  metals. 


LECLANCHfi'S  AGGLOMEKATE  BATTEKY. 

The  preceding  battery  has  not  realized  the  expecta- 
tions of  the  inventor.  It  happened  that  the  internal  re- 
sistance of  the  element  increased  considerably,  and  that 
consequently  the  battery  gave  very  unsatisfactory  results, 
especially  in  circuits  of  little  resistance. 

With  a  view  to  remedying  this  inconvenience,  Le- 
claiiche  caused  the  agglomerate,  of  which  we  have  spo- 
ken, to  be  made  in  the  shape  of  small  bricks  and  com- 
pressed in  a  hydraulic  press.  These  little  bricks  are 
placed  one  on  each  side  of  the  carbon  electrode  which 
rises  above  them  ;  they  are  held  in  this  position  by  rub- 
ber bands,  which  at  the  same  time  hold  the  rod  of  zinc 
and  the  intervening  piece  of  wood. 

"  In  the  old  battery,"  says  Leclanche,  "  the  internal  re- 
sistance depends  upon  the  conductivity  of  the  agglomer- 
ated mass  and  upon  the  adherence  of  the  carbon  in  this 
mass."  The  new  disposition  does  away  with  the  inequali- 
ties that  this  contact  produced  in  the  resistance,  and  which 
were  the  result  of  the  production  of  ammonia  in  the  interior 
of  the  agglomerate  at  the  contact  with  the  carbon  pole. 
Consequently  in  the  new  battery  the  resistance  only  de- 
pends "  upon  the  conductivity  of  the  liquid  excitant. 
This  conductivity  rather  tends  to  increase  than  to  diminish; 
in  effect,  by  the  working  of  the  battery,  chloride  of  zinc, 
which  is  a  very  good  conductor,  is  formed ;  it  is  only  the 
depolarizing  power  of  the  agglomerate  pressed  against  the 
carbon  which  varies." 

Besides,  by  increasing  the  number  of  these  little  bricks 


192  TWO-LIQUID   BATTERIES. 

placed  against  the  carbon,  the  internal  resistance  of  the 
element  maybe  diminished  at  pleasure.  Leclanche  some- 
times puts  one,  sometimes  two  as  shown  in  Fig.  45,  and 
sometimes  three. 

An  incontestable  advantage  of  the  new  battery  is  that 


FIG.  45. 


the  same  elements  may  be  employed  indefinitely,  and  it 
is  only  necessary  to  renew  the  zinc  and  the  agglomerated 
bricks  when  they  are  worn. 


OXIDES   IN   BATTERIES.  193 


CLARKE  AND   MUIRHEAD'S   MODIFICATION 
OF  LECLANCHfi'S  BATTERY. 

The  only  difference  between  this  battery  and  that  of 
Leclanche  is  that  in  the  former  the  carbon  electrode 
and  indeed  the  pieces  of  carbon  mixed  with  the  bioxide 
of  manganese  are  platinized  This  is  certainly  a  very 
good  idea,  as  we  mentioned  when  speaking  of  Smee's  and 
of  Walker's  batteries.  The  polarization  is  thus  undoubt- 
edly diminished. 

According  to  information  given  by  the  inventors,  this 
new  cell,  after  working  one  minute  in  a  circuit  of  100 
units  of  resistance,  only  loses  1  per  cent  of  its  electro- 
motive force  by  polarization,  whereas  Leclanche's  cell 
loses  2^  per  cent. 

After  five  minutes  the  platinized  cell  only  loses  2  per 
cent,  while  the  Leclanche  loses  5  per  cent. 

After  ten  minutes  the  first  one  again  loses  2  per  cent, 
and  the  second  10  per  cent ;  if  the  experiment  be  con- 
tinued, the  electro-motive  force  of  the  Leclanche  cell  is 
seen  to  diminish  steadily,  while  that  of  the  platinized  cell 
remains  constant. 

Tins  platinized  cell  has  what  we  have  termed  the  re- 
versed form  ;  that  is,  the  zinc  is  in  the  centre,  and  in  a  jar 
'which  is  not  porous,  but  whose  walls  are  pierced  with 
holes  by  which  the  communication  between  the  two  ele- 
ments is  established. 

The  zinc  has  the  form  of  quite  a  large  cylinder,  the 
object  of  which  is  to  diminish  the  resistance.  The  de- 
polarizing mixture  is  placed  around  the  sides  in  the  out- 
side jar,  which  disposition  also  diminishes  the  resist- 
ance. 


194  TWO-LIQUID   BATTERIES. 

The  outside  jar,  as  well  as  that  in  the  centre,  is  closed 
with  cement,  so  that  all  evaporation  is  prevented. 

All  these  dispositions  had  been  already  tried,  and  the 
only  new  idea  is  the  platinizing  of  the  carbon. 

The  inventors  say  that  they  sometimes  platinize  the 
fragments  of  peroxide  of  manganese.  It  would  be  inter- 
esting to  examine  closely  the  advantages  or  inconveniences 
of  this  process ;  it  might  be  inquired  whether  or  not  the 
bioxide  of  manganese  would  lose  its  efficiency  when  cov- 
ered with  platinum. 

ELECTKO-MOTIVE  FOECE.    POLAEIZATIOK 

Leclanche  represented  his  original  cell,  with  the  porous 
jar,  as  having  an  electro-motive  force  equal  to  1.38  (Dan- 
iell=l).  These  figures  are  certainly  inferior  to  the  real 
value,  at  least  before  any  polarization. 

We  will  admit  the  figures  1.48  as  given  by  Clark  and 
Sabine,  which  is  a  little  less  than  that  of  Marie  Davy's 
cell.  If  the  circuit  in  which  Leclanche's  battery  works  has 
a  considerable  resistance,  polarization  is  very  slow. 

CHEMICAL  ACTION. 

Leclanche  represents  the  chemical  action  which  takes 
place  in  his  cell  by  the  following  equation : 

]STH3HC1  +  2MnO,+  Zn  =  ZnCl  +  NH.+  HO  +  Mn2O3 

The  zinc  combines  writh  the  chlorine  of  the  ammonia 
hydrochlorate  and  forms  chloride  of  zinc ;  ammonia  is  set 
free ;  the  hydrogen  given  off  under  these  actions,  and  which 
would  polarize  the  carbon  without  the  presence  of  the 
bioxide  of  manganese,  becomes  oxidized,  forming  water, 
and  the  peroxide  is  reduced  to  sesquioxide  of  manganese. 


OXIDES   IN   BATTEEIES.  195 

If  it  be  agreed  to  give  the  name  of  chloride  of  ammo- 
nium to  that  salt  which  we  have  called  ammonia  hydro- 
chlorate,  there  would  in  reality  be  nothing  changed,  but 
its  formula  would  be  NH4C1.  It  could  be  said  that  the 
zinc  is  substituted  for  the  ammonium,  that  the  ammonium 
is  decomposed  into  ammonia  and  into  hydrogen,  etc.  etc. ; 
but  this  manner  of  expression  should  be  preferred  here, 
for  Leclanche  has  established  that  the  ammonium  acts 
more  favorably  in  the  presence  of  the  bioxide  of  man- 
ganese than  the  hydrogen  alone  would ;  it  is  indeed  for 
this  reason  that  sal  ammoniac  ought  to  be  preferred  to 
other  alkaline  chlorides,  such  as  chloride  of  potassium, 
chloride  of  sodium. 

We  ought  to  say,  however,  that  this  theoretical  reac- 
tion in  Leclanche's  battery  is  not  the  only  one  that  takes 
place.  First,  it  is  plain  that  when  the  battery  polarizes, 
it  is  undoubtedly  because  the  hydrogen  is  deposited  upon 
the  carbon  and  does  not  oxidize  at  the  expense  of  the  bi- 
oxide of  manganese.  Then  is  made  manifest  the  forma- 
tion of  double  salts,  oxy chloride  of  zinc,  and  double  chlo- 
ride of  zinc  and  ammonium.  These  salts  are  but  slightly 
soluble  and  obstruct  the  action.  A  saturated  solution  of 
sal  ammoniac  is  needed  to  dissolve  them,  which  explains 
one  of  the  practical  recommendations  made  above. 

We  are  thus  again  led  to  remark  upon  the  complicated 
nature  of  the  chemical  actions  in  batteries,  and  to  say  with 
Mr.  Gladstone  "that,  since  the  elucidation  of  the  tele- 
graph, batteries  have  been  studied  more  from  a  mechanical 
and  electric  point  of  view  than  from  a  chemical  stand- 
point, .  .  ,  and  that  there  is  much  left  to  be  done 
in  regard  to  this  matter." 

It  is  seen  from  the  theoretical  equation  of  the  battery 
that  ammonia  is  set  free,  and  that  is  what  the  experiment 


196  TWO-LIQUID  BATTEEIES. 

shows ;  but  in  the  ordinary  practice  of  the  telegraph  the 
work  is  so  intermittent,  and  the  corresponding  chemical 
actions  so  slow,  that  no  odor  of  ammonia  is  noticed  at  all. 

It  should  here  be  repeated  that  Leclanche  did  not  choose 
sal  ammoniac  by  chance.  He  tried  sea-salt  (chloride  of 
sodium)  and  chloride  of  potassium,  and  he  has  shown  that 
they  are  all  very  inferior  to  the  sal  ammoniac. 

Any  one  can  make  the  experiment  with  sea-salt  and 
show,  as  we  have  done,  that  the  electro-motive  force  of 
the  battery  thus  modified  is  very  much  less  than  that  of 
the  Leclanche  battery  properly  so-called,  and  that  it  polar- 
izes rapidly.  Consequently,  if  in  any  emergency  the 
battery  has  to  be  charged  with  sea-salt  instead  of  sal  am- 
moniac, and  a  sufficient  current  is  obtained,  it  must  not 
be  believed  that  a  new  invention  has  been  made,  nor  even 
a  good  one. 

WEAKENING  OF  THE  LECLANCHfi 
BATTEKY. 

The  bioxide  of  manganese  does  not  produce  complete 
depolarization ;  and  if  the  resistance  of  the  outside  cir- 
cuit is  very  small,  the  electro-motive  force  diminishes  rap- 
idly. It  is  only  necessary  to  close  one  of  Leclanche's 
cells  upon  itself  for  a  few  seconds  to  polarize  it  in  an  ap- 
preciable manner.  But  if  the  current  be  interrupted 
after  a  short  time,  the  battery  will  soon  recover  its  initial 
force.  This  is  the  phenomenon  of  polarization  in  all  its 
simplicity.  If  the  battery  only  works  intermittingly,  as 
in  the  telegraph  in  general,  there  is  very  little  polariza- 
tion, in  which  case  the  battery  is  perfectly  irreproachable, 
and  deserves  to  be  preferred  to  those  of  Daniell  and  of 
Marie  Davy. 


OXIDES   IN   BATTERIES.  197 

If,  on  the  other  hand,  the  Leclanche  battery  be  made  to 
work  uninterruptedly,  its  electro-motive  force  is  seen  to 
decrease  in  a  manner  very  interesting  to  watch. 

Gaugain  has  studied  this  weakening  under  conditions 
well  determined  by  measurements  of  the  intensity  of  the 
current. 

The  following  are  the  results : 

Electro-motive  Force. 

At  the  start,  May  28th 288 

June    1st 213 

Aug.    6th 199 

Sept.     2d 180 

"       3d 152 

This  weakening  would  have  been  more  rapid  had  the 
resistance  of  the  circuit  been  less,  and  less  rapid  with  a 
greater  resistance. 


PKACTICAL  DUEABILITY   OF  THE   LE- 
CLANCHfi  BATTEKY. 

We  have  said  several  times  that  this  battery  possesses 
the  great  advantage  of  dispensing  with  all  care  during 
long  periods,  on  condition,  however,  that  it  only  be  em- 
ployed for  those  purposes  for  which  it  is  suited. 

We  ought  again  to  speak  of  this  very  important  sub- 
ject. 

The  principal  French  railway  companies  have  furnished 
us  with  the  following  official  and  incontestable,  though 
very  astonishing,  information : 

A  battery  at  Y  furnishes  a  continuous  current,  causing 
an  electric  bell  to  ring  about  twenty-three  hours  every  day ; 
it  has  needed  no  care  during  eleven  months. 

When  the  batteries  at  E,  at  Y,  and  at  M  were  exam- 


198  TWO-LIQUID   BATTERIES. 

ined  in  1876,  zincs  were  still  found  which  had  been  placed 
there  in  1867. 

Finally,  a  battery  at  O  worked  from  July  26th,  1867, 
to  August  12th,  1876 ;  being  recharged  at  that  date,  the 
zincs  were  renewed  before  there  was  any  absolute  neces- 
sity. During  those  nine  years  of  service  the  sal  ammo- 
niac was  only  renewed  once,  and  this  is  the  only  expense 
occasioned  by  that  which  may  be  considered  as  the  aver- 
age work  of  a  railway  station.  This  is  the  most  striking 
example  that  has  been  given  to  us,  and  it  leads  one  to 
believe  that  it  would  be  difficult  to  imagine  a  better  bat- 
tery for  branch  offices  than  that  of  Leclanche. 

It  is  understood,  of  course,  that  these  extraordinary  pe- 
riods of  duration  are  obtained  by  intelligent  attention,  or 
rather  by  the  ^absence  of  any  carelessness  or  misunder- 
standing. The  battery  at  O  was  never  touched  except  by 
the  superintendent  of  the  telegraph,  who  followed  the 
experiment  with  great  interest. 

The'  best  telegraph  service  is  to  be  found  in  those  of- 
fices where  the  least  (Quantity  of  sal  ammoniac  is  consumed. 
An  intelligent  inspector  would  always  be  able  to  distin- 
guish the  causes  of  the  numerous  hesitations  in  the  tele- 
graph, and  act  accordingly;  whereas  another  would  at- 
tribute every  failing  to  the  weakening  of  the  battery,  and 
would  inconsiderately  hasten  to  remedy  it  by  adding  too 
great  a  quantity  of  salt. 

We  ought  here  to  point  out  the  mistaken  idea  of  the 
necessity  of  moving  the  battery  to  increase  its  force ;  some 
think  it  well  to  shake  it  in  order  to  awaken  it,  as  they 
would  do  a  person  asleep.  This  is  a  great  mistake  in  the 
management  of  the  Leclanche  battery,  which,  it  is  recom- 
mended, should  be  kept  perfectly  quiet. 

We  have  already  had  occasion  to  say  that  the  best  place 


OXIDES   IN   BATTERIES.  199 

for  a  telegraph  battery,  or  for  one  doing  analogous  work, 
is  a  cellar  in  which  the  temperature  varies  but  slightly ; 
we  can  only  repeat  this  piece  of  advice  at  present.  The 
heat  in  offices  is  rather  injurious,  as  it  occasions  an  active 
evaporation. 


CHAPTER  VII. 
CHLORIDE   BATTERIES. 

THE  depolarization  of  the  conducting  electrode  is 
generally  effected  by  oxygen,  but  it  can  also  be  done  by 
chlorine,  as  will  be  seen  in  the  batteries  which  we  will 

now  describe. 

• 

CHLOEIDE  -  OF  -  PLATINUM  B ATTEK Y. 

We  only  mention  this  battery,  not  admitted  in  prac- 
tice, because  Daniell  points  it  out  as  a  model  of  a  perfect 
battery.  After  having  described  his  sulphate-of-copper 
battery,  he  adds : 

"  The  surface  of  the  conducting  electrode  is  thus  per- 
petually renewed  by  the  deposit  of  pure  copper,  and  the 
contrary  action  of  the  zinc  and  of  every  other  metal  pre- 
cipitated is  successfully  prevented.  The  affinity  of  the 
copper  for  the  acid,  though  less,  exists,  however,  and  this 
opposition  could  not  be  prevented  except  by  the  use  of 
platinum  electrodes,  whose  surface  would  be  continually 
renewed  by  the  decomposition  of  chloride  of  platinum ; 
this  apparatus  would  be  perfect,  but  very  costly,  ..." 

It  is  probable  that  Daniell  intended  the  cell  to  be  com- 
posed as  follows :  zinc,  dilute  sulphuric  acid  ;  chloride  of 
platinum,  platinum. 

Under  these  conditions,  the  depolarization  would  be 
effected  as  in  the  Daniell  cell,  only  that  the  hydrogen 
would  be  burnt  by  the  chlorine  instead  of  by  the  oxygen. 


CHLORIDE  BATTERIES.  201 

The  principal  action  of  the  battery  would  still  be  that  of 
the  sulphuric  acid  upon  the  zinc,  and  the  decomposition 
of  the  chloride  of  platinum  would  be  less  of  an  obstacle 
to  the  principal  action  than  that  of  the  sulphate  of  copper 
in  the  Daniell.  The  electro-motive  force  of  the  chloride- 
of -platinum  battery  ought  to  be  much  greater  than  that 
of  the  sulphate-of -copper  battery. 

CHLOKIDE-OF-SILYEK  BATTEKY. 

Marie  Davy  appears  to  have  been  among  the  first  to 
employ  chloride  of  silver.  In  1860  he  wrote  the  fol- 
lowing : 

"  I  have  constructed  a  battery  formed  of  zinc,  pure 
water,  and  chloride  of  silver  melted  in  a  silver  crucible, 
and  it  has  worked  witli  perfect  regularity.  Its  internal 
resistance,  at  first  very  great,  has  gradually  diminished  in 
proportion  as  the  chloride  of  zinc  formed  has  been  dis- 
solved in  the  water.  By  previously  dissolving  this  salt, 
the  battery  immediately  furnishes  a  strong  current.  The 
chloride  of  silver  is  completely  reduced  throughout  all  its 
parts,  always  preserving  its  shape.  The  insolubility  of 
the  reducible  salt  becomes  an  advantage,  as  it  dispenses 
with  the  use  of  porous  jars.  ..." 

During  the  same  year  we  studied  this  battery,  using 
a  porous  jar  and  undissolved  chloride  of  silver ;  our  elec- 
trodes were  of  copper  and  amalgamated  zinc.  We  found 
the  electro-motive  force  to  be  apparently  equal  to  that  of 
the  Daniell. 

These  experiments  possess  in  themselves  but  little 
interest.  It  is  only  since  "Warren  De  La  Hue  has  given 
his  attention  to  this  battery  that  it  has  attained  any  impor- 
tance, and  that  its  use  has  become  general. 


202  TWO-LIQUID   BATTERIES. 

In  the  beginning  of  his  researches,  this  physicist  used 
chloride  of  silver  in  the  shape  of  a  powder  or  paste,  and 
his  liquid  was  a  thin  solution  of  sea-salt.  A  little  incon- 
venience in  this  battery  has  been  pointed  out  to  us.  It 
appears  that  it  evolves  gas,  and  that,  consequently,  if  the 
glass  jar  be  hermetically  closed  the  pressure  of  the  gas 
causes  it  to  burst. 

It  is  clear  that  this  gas  is  only  an  inconvenience  when 
the  jars  are  tightly  closed,  and  that  its  gravity  should  not 
be  exaggerated. 

At  all  events,  we  believe  that  the  form  which  De 
La  Rue  has  given  to  the  battery  does  not  present  this 
little  disadvantage,  and  that  it  contains  several  very  inter- 
esting dispositions.  Figure  46  represents  a  battery  of  ten 
cells,  each  of  which  is  composed  in  the  following  manner : 

The  outside  cylindrical  jar  is  about  5  in.  high  and 
1J  in.  in  diameter.  The  soluble  electrode  is  formed  of  a 
rod  of  unamalgamated  zinc,  but  of  very  good  quality.  In 
the  upper  part  of  this  zinc  rod  is  bored  a  hole,  in  which 
a  strip  of  silver  (positive  connection  of  the  adjoining  cell) 
is  held  by  means  of  a  small  brass  wredge,  which  assures 
a  perfect  contact  between  the  zinc  and  the  silver. 

The  other  electrode  is  formed  of  a  strip  of  silver 
around  which  is  melted  a  cylinder  of  chloride  of  silver, 
AgCl,  represented  separately  in  the  figure. 

To  avoid  an  accidental  contact  of  the  two  electrodes, 
the  rod  of  chloride  of  silver  is  placed  in  a  small  cylinder 
of  parchment  paper,  A  ;  there  are  two  holes  near  the  top 
of  this  paper  cylinder,  through  which  the  strip  of  silver 
passes,  as  shown  in  B. 

The  liquid  is  a  diluted  solution  of  sal  ammoniac ;  the 
best  proportion  is  that  of  23  grammes  of  chloride  of 
ammonium  to  1  litre  of  distilled  water. 


CHLORIDE   BATTEEIES. 

0 


203 


FIG.  46. 


204  TWO-LIQUID   BATTERIES. 

The  outside  jar  is  closed  with  a  paraffin  stopper  through 
which  the  zinc  passes  ;  the  strip  of  silver  passes  between 
the  stopper  and  the  glass  jar.  The  figure  also  shows  that 
there  is  a  hole  made  in  the  paraffin  stopper,  through 
which  the  liquid  is  poured  in  by  means  of  a  small  fun- 
nel, and  then  the  hole  is  closed  writh  a  small  paraffin  cork. 

The  choice  of  this  material  presents  important  advan- 
tages. First,  paraffin  is  one  of  the  best  insulating  sub- 
stances, which  is  of  great  importance  wrhen  several  thou- 
sand cells  are  joined  in  intensity,  as  De  La  Rue  does. 
Then  it  is  absolutely  antihygrometric,  so  that  if  a  little 
water  be  dropped  upon  its  surface  it  collects  in  many 
little  globules  and  does  not  spread  over  the  surface,  which 
might  destroy  the  insulation.  The  air  does  not  deposit  it- 
self upon  it  as  upon  glass,  for  instance,  whose  surface 
thus  covered  with  steam  becomes  a  conductor.  Finally, 
paraffin  melts  when  slightly  heated.  The  jar  may  be  her- 
metically closed  by  means  of  a  small  iron  wire,  flattened 
at  the  end  and  slightly  heated,  which  is  passed  around 
the  zinc  where  it  comes  through  the  cork,  and  also  around 
the  paraffin  stopper  which  closes  the  orifice  for  the  intro- 
duction of  the  liquid. 

The  action  in  this  battery  is  very  simple :  the  zinc  is 
dissolved  and  takes  the  place  of  the  silver  in  the  chloride ; 
the  silver  is  deposited  in  a  porous  mass  first  upon  the 
surface  and  then  in  the  mass  of  the  chloride. 

The  capital  advantage  of  this  battery,  as  in  all  where 
zinc  with  sal  ammoniac  is  used,  consists  in  the  absence  of 
any  local  or  internal  action  as  long  as  the  electric  circuit 
is  open  ;  in  other  words,  this  battery  does  not  work  upon 
itself.  This  circumstance  is  very  important,  for  these 
cells  are  only  used  in  experiments  of  short  duration  and 
long  intervals ;  it  is  necessary  to  find  the  battery,  eight 


CHLORIDE   BATTERIES.  205 

days  later,  in  exactly  the  same  state  in  which  it  was  left 
eight  days  previous. 

In  the  first  moments  of  the  action  the  current  is  very 
feeble  ;  this  is  caused  by  the  great  resistance,  for  the  con- 
ductivity of  the  chloride  of  silver  is  very  little  and  the 
exposed  surface  of  the  silver  electrode  is  very  small. 
But  at  the  end  of  a  certain  time  the  surface  of  the  chlo- 
ride is  covered  with  silver,  its  conductivity  is  increased, 
and  the  intensity  attains  its  normal  value,  which  varies 
but  little  afterwards,  as  is  shown  by  the  following  table 
of  experiments  made  by  De  La  Rue  with  a  voltameter : 

Gas  per  Minute. 

At  the  start,  June  29th,  1875 1     cent.  cube. 

July  4th,         "    1.4     " 

Oct,  27th,        "    1.4     " 

March  15th,  1876 1.45  "  '     " 

April  8th,       "    1.41  " 

The  electro-motive  force  of  these  cells  differs  very  little 
from  that  of  the  Daniell.  De  La  Eue  found  it  to  be  0.97 
with  sea  salt,  and  1.03  with  sal  ammoniac. 

The  resistance  is  about  4.3  ohms,  as  nearly  as  could  be 
ascertained. 

For  the  above-mentioned  experiments  De  La  Hue  col- 
lects 200  cells  upon  a  single  board ;  they  pass  through  a 
slab  of  ebonite,  which  is  a  better  insulator  than  wood. 

Six  of  these  batteries  of  200  cells  each  are  placed  one 
above  the  other  in  a  carefully  constructed  closet  which 
protects  them  from  dust  or  from  accidents. 

This  is  not  the  place  to  enlarge  upon  De  La  Hue's  ex- 
periment. We  would  only  say  that  he  has  again  proved 
that  electricity  generated  by  batteries  differs  in  no  way 
from  that  generated  by  electric  machines,  and  that  if  a 
sufficient  number  of  cells  be  joined  to  form  a  battery,  a 


206  TWO-LIQUID   BATTERIES. 

continuous  spark  is  observed  when  the  extremities  of  the 
two  connections  are  brought  in  close  proximity  to  each 
other.  De  La  Rue  has  collected  as  many  as  8000  cells  in 
one  battery,  many  more  than  any  one  had  previously  col- 
lected, and  he  proposes  soon  to  make  a  battery  of  12,000 
cells. 

There  can  be  no  polarization  in  the  experiments  made 
by  this  physicist,  as  they  last  but  a  short  time  and  are 
made  at  such  long  intervals,  as  is  the  case  in  nearly  all 
purely  scientific  experiments.  But  Du  Moncel  has  made 
some  direct  experiments  which  prove  that  after  the  cir- 
cuit has  been  closed  twenty  hours  the  battery  shows  no 
polarization  ;  and  if,  in  fact,  the  action  takes  place  as  we 
have  said — that  is,  the  simple  substitution  of  zinc  for  sil- 
ver in  the  chloride — there  is  no  hydrogen  set  free,  and 
consequently  no  polarization.  As  the  deposit  of  silver 
upon  the  conducting  electrode  does  not  change  the  na- 
ture of  the  latter,  the  conditions  are  the  same  as  in  the 
Daniel!  battery,  which  is  the  model  of  completely  depo- 
larized batteries. 

GAIFFE'S  BATTEKY. 

The  chloride-of-silver  battery  is  very  extensively  used 
by  Gaiffe  for  induction-coils  or  to  furnish  continuous  cur- 
rents used  for  medicinal  purposes. 

His  cells  are  very  small  and  hermetically  closed  in 
ebonite  boxes  having  screw  tops. 

In  those  batteries  which  are  destined  to  be  transported 
frequently  from  one  place  to  another  there  is  no  free 
liquid ;  the  two  electrodes  are  separated  by  six  or  eight 
sheets  of  blotting-paper  saturated  with  a  solution  contain- 
ing 5  per  cent  of  chloride  of  zinc. 


CHLORIDE  BATTERIES. 


207 


Gaiffe  lias  employed  powdered  chloride  of  silver,  but 
he  now  seems  to  prefer  the  melted  chloride. 

The  residue  of  the  battery  is  silver,  and  if  it  be  kept 
and  given  back  to  the  manufacturer  its  use  is  very 
economical. 

Figure  47  represents  another  cell  which  stands  on  end, 
and  in  which  liquid  is  placed  as  in  ordinary  batteries. 

The  electrodes  are,  as  is  seen,  attached  to  metallic  pieces 


FIG.  47. 


which  pass  through  the  top,  and  to  which*  are  fastened 
the  connections  of  the  adjoining  cells. 

There  is  no  waste  in  these  batteries  when  the  circuit  is 
open,  which  is  of  great  advantage.  It  is  important  to 
note  that,  in  order  not  to  lose  this  advantage,  the  top  must 
be  kept  perfectly  dry,  for  the  least  humidity  that  might 
join  the  electrodes  would  establish  a  circuit  and  produce 
a  constant  working  in  the  cell. 


208  TWO-LIQUID   BATTERIES. 


CHLOEIDE-OF-LEAD  BATTEEY. 

Marie  Davy  tried  the  use  of  chloride  of  lead,  but  the 
electro-motive  force  thus  obtained  was  less  than  the  unit 
(Darnell's  cell).  There  is  therefore  no  advantage  in  its 
use,  for  chloride  of  lead  is  comparatively  dear. 


PEECHLOEIDE-OF-IEOX  BATTEEY. 

In  1866  Ducliemin  proposed  the  use  of  perchloride  of 
iron  as  depolarizing  agent.  This  substance  is  pointed  out 
as  containing  a  quantity  of  chlorine,  as  are  the  peroxides 
of  lead  and  of  manganese,  which  contain  large  quantities 
of  oxygen. 

The  battery  in  question  has  an  electrode  of  zinc  im- 
mersed in  a  solution  of  sea-salt,  and  an  electrode  of  car- 
bon in  a  solution  of  perchloride  of  iron. 

The  hydrogen  given  off  by  the  action  of  the  zinc  upon 
the  water  goes  straight  to  the  carbon  and  decomposes  the 
iron  salt,  which  is  transformed  into  protochloride. 

The  hydrochloric  acid,  formed  by  the  combining  of 
the  polarizing  hydrogen  and  the  chlorine  set  free  from 
the  perchloride,  contributes  to  the  dissolving  of  the  zinc 
and  to  the  intensity  of  the  battery. 

This  cell  is  not  constant ;  first  because  depolarization,  is 
not  complete,  and  again  because  there  are  deposits,  pos- 
sessing little  conductivity,  made  upon  the  zinc. 

Du  Moncel  has  shown  that  the  electro-motive  force  of 
this  battery  is,  at  first  starting,  very  superior  to  that  of 
Marie  Davy's  battery,  and  inferior  to  that  of  Bunsen's 
battery. 


CHLORIDE   BATTERIES.  209 

The  figures  are : 

Bunsen  or  Grove  cell 11,123 

Perchloride  of  iron 9,640 

Marie  Davy's  sulphate -of -mercury  cell 8,192 

The  contrivance  proposed  by  Ducliemin  would  there- 
fore appear  worthy  of  study.  It  is  probable  that,  by 
means  of  some  chemical  or  physical  artifices,  the  con- 
stancy of  this  battery  might  be  increased. 

The  mixture  of  pieces  of  carbon  with  the  perchloride 
of  iron  has  already  been  tried,  and  with  good  results. 


CHAPTER  VIII. 
DEPOLARIZING -MIXTURE  BATTERIES. 

WE  have  seen  in  the  previous  chapters  that  the  constant 
preoccupation  of  physicists  should  be  to  depolarize  the 
conducting  electrode  by  surrounding  it  with  those  bodies 
from  which  oxygen  or  chlorine  is  easily  freed.  These 
gases  combine  witli  the  gases  evolved  by  the  action  of 
the  battery,  and  prevent  or  diminish  the  polarization  of 
the  electrode.  Instead  of  employing  bodies  which  furnish 
oxygen  or  chlorine  by  their  decomposition,  a  mixture  of 
two  substances,  whose  reciprocal  reaction  produces  oxygen 
or  chlorine,  may  be  placed  around  the  electrode. 

A  battery  may  therefore  be  made  by  using  any  of  the 
means  indicated  in  works  upon  chemistry  for  the  prepara- 
tion of  oxygen  or  chlorine. 

We  will  examine  the  most  important  of  these  batteries, 
commencing  with  those  in  which  oxygen  is  the  depolariz- 
ing agent. 

POTASSIUM -CHLOEATE  AND   SULPHUKIC- 
ACID  BATTEKY. 

In  1859  Messrs.  Salleron  and  Renow  presented  to  the 
French  Academy  of  Sciences  a  battery  in  which  depolari- 
zation was  effected  by  means  of  a  mixture  of  potassium 
chlorate  and  dilute  sulphuric  acid. 

This  battery  appears  not  to  have  been  used  except  in  a 
few  experiments  made  by  the  inventors.  Its  failure,  how- 


DEPOLAKIZING-MIXTUKE  BATTERIES.  211 

ever,  may  have  been  due  to  some  secondary  cause,  and  wd 
believe  that  the  idea  might  be  carried  out,  and  with  very 
good  results. 

The  electro-motive  force  of  this  battery  is  less  than  that 
of  Grove's  cell,  but  greater  than  that  of  the  Daniell. 

The  inventors  call  attention  to  the  fact  that  the  potas- 
sium chlorate  destroys  live  times  the  quantity  of  hydrogen 
that  sulphate  of  copper  does,  and  that  its  cost  is  only 
about  three  times  greater,  whence  their  justifiable  con- 
clusion that  the  battery  ought  to  be  economical. 

Unfortunately  we  have  not  been  able  -to  ascertain 
whether  the  depolarization  is  complete  or  not ;  we  have 
not  had  time  to  make  the  experiment  ourselves. 

ANALOGOUS  CONTKIVANCES. 

Potassium  chlorate  could  be  replaced  by  chlorate  of 
sodium,  and  the  chlorates  by  the  nitrates. 

The  mixture  of  nitrate  of  sodium  and  sulphuric  acid 
has  been  tried,  and  it  presents  several  economical  advan- 
tages, because  nitrate  of  sodium  is  a  very  cheap  salt  found 
in  large  quantities  in  South  America. 

We  do  not  believe  that  this  battery  has  ever  been  used 
in  the  practice,  but  we  do  not  know  what  disadvantages 
it  might  possess. 

BICHKOMATE- OF -POTASSIUM  AND   SUL- 
PHURIC-ACID BATTEEIES. 

Among  the  many  known  means  for  the  preparation  of 
oxygen,  there  is  one  which  consists  in  putting  bichromate 
of  potassium  and  acidulated  water  in  a  retort.  The  reac- 
tion is  indicated  by  the  following  equation : 


212  TWO-LIQUID   BATTERIES. 

KO.2CrO3  +  4S03  =  O2O3,  3SO3  +  KO.SO,  +  O, 

That  is,  an  alum  (double  salt  having  the  formula 
Cr2O3, 3SO3  +  KO.SO3)  and  oxygen  are  formed. 

The  use  of  this  mixture  for  depolarizing  the  conducting 
electrode  was  an  idea  of  Poggendorff,  who  thus  conceived 
a  very  interesting  voltaic  combination,  which  has  received 
many  applications  under  the  great  variety  of  forms  given 
to  it  by  the  constructors. 

The  most  simple  form  of  this  cell  is  the  same  as  that  of 
the  Bunsen  :  amalgamated  zinc  in  a  glass  or  earthenware 
jar,  porous  jar  in  the  centre  of  the  zinc  cylinder,  carbon 
in  the  porous  jar.  In  the  outside  jar  is  sulphuric  acid 
diluted  with  twelve  times  its  weight  of  water.  In  the 
porous  jar  is  a  mixture  composed  as  follows : 

100  parts  of  water. 
12     "      "  bichromate  of  potassium. 
25    "      "  sulphuric  acid. 

This  battery  thus  charged  has  an  electro-motive  force 
greater  than  that  of  any  battery  that  we  have  as  yet 
studied ;  it  is  equal  to  2028  volts,  according  to  Clark 
and  Sabine,  which  means  that  it  is  double  that  of  the 
Daniell  cell. 

It  is  true  that  "W.  H.  Preece,  Electrician  of  the  Post- 
office,  England,  found  it  to  be  equal  to  1.97  at  its  maxi- 
mum, with  a  liquid  composed  a  little  differently,  of  which 
we  will  speak  as  we  proceed.  But  even  admitting  this 
latter  value,  it  is  seen  that  the  electro-motive  force  of  the 
battery  in  question  is  greater  than  that  of  either  Grove's 
or  Bunsen's  battery. 

It  must  be  added  that  this  extraordinary  electro-motive 
force  is  only  realized  at  first  starting,  for  the  battery 
polarizes  rapidly,  at  least  if  placed  in  a  very  short  circuit. 


DEPOLARIZING-MIXTURE   BATTERIES.  213 

The  conclusion  to  be  drawn  from  this  last  observation 
is  that  PoggendorfFs  depolarizing  mixture  accomplishes 
but  incompletely  its  object ;  for  this  reason  his  idea, 
however  ingenious  it  may  be,  cannot  be  placed  side  by 
side  with  the  inventions  of  Daniell  or  Grove. 

It  is  important  to  note  that  the  two  substances  of 
which  the  mixture  is  composed  act  upon  each  other  inde- 
pendently of  any  action  of  the  battery  ;  consequently  the 
liquid  ceases,  after  a  certain  time,  to  possess  any  depolar- 
izing virtue.  In  1841  Bunsen  suggested  a  much  more 
complex  mixture  of  chromate  of  potash,  chloride  of  potas- 
sium, bioxide  of  manganese,  and  common  salt.  Wiede- 
mann  says  that  this  mixture  gives  less  satisfactory  results 
than  that  suggested  later  by  Poggendorff. 

CHEMICAL    ACTION    IN    THE    BICHKOMATE 
BATTEKY. 

Poggendorff  gives  the  following  as  the  composition  of 
the  mixture  to  be  placed  around  the  carbon  : 

Bichromate  of  potash 3  parts. 

Sulphuric  acid 4     " 

Water 18     " 

Another  composition,  as  suggested  by  Wohler  and  Buff, 
is: 

Bichromate  of  potash 12  parts. 

Sulphuric  acid 25     " 

Water 100      " 

It  is  with  this  latter  mixture  that  the  measurements  for 
the  electro-motive  force  stated  above  were  taken,  and  it 
is  that  which  is  used  in  the  German  telegraphs. 

Many  other  proportions  have  been  suggested,  and  there 


214  TWO-LIQUID    BATTERIES. 

prevails  concerning  this  subject  a  certain  confusion  which 
we  will  endeavor  to  do  away  with. 

It  should  be  well  understood  that  we  are  now  speaking 
of  batteries  of  two  liquids,  separated  by  a  porous  parti- 
tion.* 

Returning  to  the  equation  representing  the  nature  of 
the  chemical  action  produced  by  the  reaction  of  the  sul- 
phuric, acid  upon  the  bichromate  of  potash,  it  is  seen  that 
four  equivalents  of  sulphuric  acid  must  be  made  to  react 
upon  one  of  bichromate. 

Bichromate  of  potash  is  an  anhydride,  whose  equivalent 
is: 

KO ,  47.11 

2CrO3 ..100.56 


147.67 

Sulphuric  acid,  the  rnonohydrate,  has   the    following 
equivalent : 

S03 40 

HO 9 

49 

and  four  equivalents  have  a  weight  equal  to  49x4=196. 
Thus  the  theoretical  proportion  is  that  of  147  to  196, 
or  in  round  numbers  150  to  200,  which  is  that  of  3  to  4 
as  indicated  by  Poggendorff.  We  repeat  once  more  that 
it  is  the  sulphuric  monohydrate  that  we  speak  of.  If 
ordinary  commercial  sulphuric  acid  were  used,  the  propor- 
tion of  3  to  4  would  no  longer  be  in  accordance  with  the 
theory  (which  we  have  just  exposed). 

*We  will  speak  later  of  bichromate  batteries  without  porous  jar, 
which  are  termed  (wrongly,  according  to  our  idea)  single-liquid 
batteries.  The  composition  of  the  liquid  ought  to  be  different. 


DEPOLAKIZING-MIXTURE   BATTEEIES.  215 

It  must  be  admitted  that  the  proportion  as  indicated  by 
Poggendorff  has  only  a  theoretical  value,  because  the  com- 
mercial sulphuric  acid  which  is  necessarily  employed  in 
the  practice  is  not  a  monohydrate,  but  contains  more 
water. 

It  is  probable  that  Wo'hler  and  Buff  increased  the  pro- 
portion of  sulphuric  acid  because  they  found  that  an  ex- 
cess of  the  acid  facilitated  the  action ;  perhaps  they  also 
observed  that  the  conductivity  of  the  liquid  was  greater 
with  the  composition  they  suggest. 

If  we  were  studying  batteries  without  porous  jar,  the 
proportions  ought  to  be  very  different ;  the  reaction  may 
be  represented  by  the  equation  : 

3Zn  +  KO.2CrO3  +  7SO3HO  =  3ZnO.SO3  +  Cr2O33SO, 
+  KOSO.  +  THO 

Therefore,  one  equivalent  of  bichromate  of  potash 
(147.67)  and  seven  equivalents  of  sulphuric  monohydrate 
(49x7=343)  are  theoretically  necessary,  say  in  round 
numbers  3  to  7. 

Mr.  Byrne  recommends  the  following  mixture,  in  which 
the  proportion  of  sulphuric  acid  is  still  greater  than  that 
indicated  by  the  preceding  calculation : 

840  grammes  of  bichromate  of  potash. 
925        "         "  sulphuric  acid. 
2500        "         "  water  (2i  litres). 

The  proportion  of  925  grammes  of  acid  to  2500  litres 
of  water  is  greater  than  that  which  corresponds  to  the 
maximum  of  conductibility  of  the  mixture  (see  Table  IV. 
at  the  end  of  the  book).  But  it  must  be  taken  into  con- 
sideration that,  as  soon  as  the  battery  begins  to  work,  the 
acid  weakens;  therefore  it  is  quite  justifiable  to  put  a 
larger  quantity  than  is  necessary  at  first  starting. 


216  TWO-LIQUID   BATTERIES. 


APPLICATION  TO  THE  TELEGRAPH. 

The  bichromate-of-potash  battery  is  employed  in  Prus- 
sia in  very  important  offices.  Its  considerable  electro- 
motive force  has  caused  it  to  be  preferred  to  the  Daniell 
(Meidinger's  balloon  form)  in  all  places  where  there  is  an 
especial  person  to  take  care  of  it,  and  where  the  handling 
is  not  of  such  great  importance. 

On  account  of  its  great  electro-motive  force  and  its  fee- 
ble resistance,  this  battery  is  well  suited  to  those  offices 
where  work  is  done  on  several  lines  at  once  with  a  single 

O 

battery. 

"The  necessity  of  frequently  renewing  the  elements/' 
says  Dr.  Dehms,  "  is  an  inconvenience,  but  there  is  no 
difficulty  in  the  operation.  '  The  Commission '  has  in 
part  avoided  this  inconvenience  by  proposing  the  con- 
struction of  very  large  cells.  The  large  quantity  of  ma- 
terial that  they  are  able  to  hold  necessitates  a  less  fre- 
quent renewal. 

"  The  electro-motive  force  and  the  resistance  vary  in  an 
unfavorable  manner  from  the  beginning  until  the  battery 
is  completely  exhausted.  The  electro-motive  force  dimin 
ishes  but  slightly,  and  the  resistance  increases  considera- 
bly. In  order  to  obtain  a  greater  constancy,  a  certain 
number  of  elements  may  be  changed  at  regular  intervals, 
and  not  the  whole  battery  at  one  time." 

The  elements  used  by  the  German  Government  are  dis- 
posed as  has  been  described  when  speaking  of  the  Germaii 
model  of  Bunsen's  battery. 

The  carbon,  having  a  height  of  6  J  inches  and  an  exte- 
rior diameter  of  3£  inches,  is  placed  in  the  outer  jar, 
around  the  porous  jar;  its  walls  are  pierced  with  nine 


DEPOLAKIZING-MIXTUKE  BATTEEIES.  217 

lioles  at  different  heights,  in  order  to  facilitate  the  circu- 
lation of  the  liquid.  A  copper  ring  is  closely  laid  around 
the  upper  part,  which  has  previously  been  immersed  in  a 
bath  of  paraffine,  as  we  have  explained  in  speaking  of 
other  batteries,  to  prevent  the  attack  on  the  metal  by  the 
acids ;  this  ring  is  separated  from  the  carbon  by  a  thin 
strip  of  tin. 

The  zinc  is  placed  in  the  porous  jar  and  is  cross-shaped, 
which  gives  a  considerable  surface  with  a  comparatively 
small  mass. 

The  liquids  used  are :  with  the  zinc,  sulphuric  acid 
diluted  with  20  times  its  bulk  of  water ;  and  with  the 
carbon,  one  part  by  weight  of  bichromate  of  potash,  two 
parts  of  sulphuric  acid  and  eight  of  water,  the  latter  liquid 
being  the  theoretical  mixture  indicated  by  Buff. 

We  believe  it  is  well  in  this  battery  to  give  a  large  sur- 
face to  the  carbon,  and  to  place  it  in  the  outer  jar ;  the 
battery  not  being  completely  depolarized  by  the  mixture, 
there  is  an  advantage,  as  we  have  several  times  repeated, 
in  increasing  the  size  of  the  conducting  electrode.  As 
the  liquids  are  not  subject  to  evaporation,  there  is  no  in- 
convenience in  increasing  the  quantity  of  that  liquid 
which  produces  the  depolarization.  The  disadvantages  of 
the  cast-zinc  disappear  with  the  amalgamation,  at  least  if 
the  amalgam  is  renewed  frequently  enough. 

Dr.  Dehms  calls  this  a  Bunsen  battery,  with  chromic 
acid.  We  believe,  however,  basing  our  opinion  upon  the 
authority  of  "Wiedemann,  that  this  is  a  misnomer. 

GAUGAIN'S  EXPEEIMENTS. 

Gaugain  has  given  the  results  of  several  very  interest- 
ing experiments  with  bichromate-of -potash  batteries. 


218  TWO  LIQUID   BATTERIES. 

He  lias  shown  that  chrome  alum  forms  in  the  battery 
even  when  not  at  work,  but  that  the  electro-motive  force 
is  only  slightly  diminished  by  this  alteration  in  the  liquid ; 
it  only  varies  from  296  to  278  in  four  months  (open 
circuit). 

He  found  that  by  causing  the  battery  to  work  upon  an 
electric  bell  night  and  day,  the  electro-motive  force  was, 
after  17  weeks'  work,  still  superior  to  that  of  the  Daniell 
cell. 

These  figures  show  that  the  battery  in  question,  although 
less  constant  than  the  Leclanche,  is  still  a  good  battery, 
especially  when  a  large  number  of  cells  are  to  be  collected 
together  in  a  limited  space.  It  will  furnish  an  equal  cur- 
rent with  fewer  cells.  There  will  be  no  freeing  of  gases 
or  odors,  and  it  will  only  require  more  frequent  attention. 


USE  IN  ENGLAND. 
FULLER'S  BATTERY. 

The  bichromate-of-potash  battery  has  also  been  em- 
ployed in  England  since  1877,  under  a  form  giv^n  to  it 
by  Fuller.  The  zinc  plate  is  placed  upright  in  the  porous 
jar,  and  held  in  this  position  by  means  of  a  kind  of  ring 
at  the  bottom.  It  should  be  carefully  amalgamated,  as 
also  the  copper  wire  which  rises  from  the  bottom  and 
serves  as  the  connection.  Finally,  an  ounce  of  liquid 
mercury  is  put  in  the  bottom  of  the  porous  jar,  as  we  have 
seen  done  by  Tyer  and  other  electricians. 

The  carbon  does  not  surround  the  porous  jar  as  in  the 
German  model ;  it  is  a  simple  plate  6  in.  by  2  in.,  and 


DEPOLAKIZING-MIXTURE   BATTERIES.  219 

provided  with  a  metallic  cap  to  which  a  clamp  screw  is 
attached. 

We  owe  to  Mr.  Spagnoletti  some  very  interesting  infor- 
mation upon  the  results  obtained  from  the  use  (ft  this 
battery  upon  the  Great  Western  Railway,  England. 

He  estimates  its  electro-motive  force  at  2  volts  and  its 
resistance  at  1  ohm,  for  the  model  whose  capacity  is  one 
litre.  At  Paddington  Station  the  service,  directed  upon 
11  lines,  varying  from  42  to  284  miles,  is  done  at  present 
with  64  of  Fuller's  cells  only.* 

,  This  battery  worked  actively  night  and  day  the  whole 
of  the  year  1878,  during  which  time  sulphuric  acid  was 
added  ten  times  and  bichromate  only  five  times.  At 
the  end  of  December  the  cells  were  dismounted  and 
thoroughly  cleaned ;  several  zinc  plates  had  to  be  replaced. 

It  is  seen  that  the  care  of  the  battery  is  reduced  very 
much ;  and  indeed  during  the  first  three  or  four  months 
no  attention  whatever  is  necessary. 

Mr.  Spagnoletti  considers  this  battery  as  very  conve- 
nient for  branch  offices  ;  and  indeed,  when  compared  with 
the  Daniell,  the  reduction  to  one  half  of  the  number  of 
cells  is  no  small  advantage. 

The  cost  of  keeping  the  battery,  in  order  is  not  very 
great,  as  the  carbon  ought  to  last  a  long  time,  and  the 
zinc  from  twelve  to  eighteen  months  ;  the  sulphuric  acid 
and  the  bichromate  are  substances  which  cost  very  little. 

It  appears  that  there  are  already  20,000  cells  in  use  in 
England,  which  is  proof  of  a  great  success.  We  know  from 

*  It  is  interesting  to  note  that  at  Paddington  Station  64  of 
Fuller's  cells  replace  575  of  Daniell's  of  the  model  shown  in  Fig.  23. 
This  enormous  progress  is,  however,  not  wholly  due  to  the  superiority 
of  the  bichromate  battery ;  it  is  due  in  a  great  measure  to  the  adop- 
tion of  the  "Universal  System." 


220  TWO-LIQUID  BATTEEIES. 

good  authority  that  3000  cells  are  now  in  use  at  the 
General  Post-office,  London. 

The  only  new  peculiarity  we  notice  in  Fuller's  battery 
is  the  amalgamation  of  the  zinc,  which  suppresses  all  local 
actions  and  prevents  the  waste  of  the  zinc  during  the 
whole  time  the  circuit  is  open.  This  is  a  capital  advan- 
tage in  its  application  to  the  telegraph. 

This  battery  appears  to  us  to  be  well  suited  to  impor- 
tant telegraph  offices  where  the  Leclanche  is  out  of  place. 
It  also  does  very  well,  as  Mr.  Spagnoletti  says,  for  closed 
current  services. 

For  ordinary  telegraph  offices,  however,  the  Leclanch^, 
or  the  chloride-of-lime  battery,  appears  to  us  to  be  supe- 
rior. It  is  true  that  a  larger  number  of  cells  is  required, 
but  the  handling  of  any  acid  is  dispensed  with,  and  the 
battery  may  remain  many  months  without  being  visited, 
and  years  without  renewing  the  zinc. 

MILITAEY  BATTEEIES. 

Bichromate-of -potash  batteries  with  especial  dispositions 
are  used  to  set  fire  to  military  mines.  A  description  of 
them  can  be  found -in  Captain  Picardat's  book.*  We 
will  only  describe  two  of  these  apparatus. 

The  single-cell  battery,  represented  by  Fig.  48,  is  com- 
posed of  a  hollow  zinc  cylinder,  in  the  centre  of  which 
is  a  rod  of  carbon.  The  outer  surface  of  the  zinc,  which 
is  not  designed  to  effectually  contribute  to  the  useful 
action  of  the  battery,  is  painted  over  with  a  black  varnish, 
which  shields  it  from  the  attack  of  the  liquid.  The  two 
electrodes  are  fastened  to  a  small  circular  piece  of  wood, 

*  "Les  Mines  dans  la  Guerre  de  Campagne."    Picardat,  1874. 


DEPOLAKIZING-MIXTURE  BATTERIES.  221 

which  is  provided  with  terminals  to  which  the  conductors 
are  attached.  The  liquid  is  contained  in  a  glass  jar  closed 
with  a  wooden  tampion  surrounded  with  rubber. 

The  electrodes  are  only  immersed  in  the  liquid  at  the 
precise  moment  when  the  mine  is  to  be  exploded,  and 
they  only  remain  a  few  seconds.  Under  these  circum- 
stances the  battery  has  its  maximum  effect. 

If,  in  a  very  short  time  after  use,  the  electrodes  can  be 
washed  in  pure  water,  there  will  be  no  sensible  waste  of 
the  zinc ;  neither  will  any  liquid  have  been  consumed. 


FIG.  48. 

Consequently  with  a  little  care  and  attention  the  battery 
may  do  service  a  long  time  without  being  renewed  or  re- 
paired. The  whole  apparatus  is  enclosed  in  a  small  box 
with  two  compartments,  which  the  figure  plainly  shows. 
This  simple  battery  is  known  by  the  name  of  "  Arras," 
because  it  was  first  used  at  the  Ecole  regimentaire  du 
Genie  $  Arras  by  Captain  Barisien.  In  fact  this  battery 
was  originally  arranged  as  we  will  now  describe. 

During  the  siege  of  Paris,  in  1871,  batteries  of  four 


222  TWO-LIQUID   BATTERIES. 

cells  were  constructed.  Each  cell  is  composed  of  a  half 
cylinder  of  zinc  and  a  half  cylinder  of  carbon,  separated 
at  the  upper  part  by  a  little  piece  of  ebonite.  They  are 
supported  by  being  fastened  in  holes  made  in  a  small 
board ;  these  holes  may  be  lined  with  copper,  which  es- 
tablishes a  good  contact  between  the  electrodes  and  the 
connections  of  the  adjoining  cells.  A  wooden  handle 
allows  the  four  cells  to  be  moved  at  once  and  simulta- 
neously immersed  in  the  jars  containing  the  liquid.  There 
was  in  the  box  a  second  compartment  where  the  elec- 
trodes remain  separated  from  the  liquid  while  the  bat- 
tery is  not  at  work. 

We  have  described  this  apparatus  to  show  especially 
how  it  may  be  improvized,  perhaps  not  in  the  country, 
but  in  a  besieged  town  or  city,  where  there  might  be  a 
lack  of  more  perfect  material. 

GKEKET'S  BOTTLE  BATTEKY. 

This  battery  (Fig.  49)  has  the  form  of  a  bottle  with  a 
wide  mouth,  the  lower  part  being  almost  spherical.  The 
top  is  provided  with  a  brass  frame,  to  which  is  fastened 
an  ebonite  cover.  To  this  cover  are  attached  two  carbon 
plates  which  permanently  dip  into  the  liquid,  and  which 
are  held  apart  at  the  bottom  by  means  of  small  pieces  of 
ebonite.  Between  the  carbon  plates  is  suspended  a  zinc 
plate  which  may  be  plunged  into  the  fluid  or  withdrawn 
at  pleasure.  The  contact  between  the  carbon  and  the  zinc 
is  prevented  by  little  pieces  of  ebonite  fastened  to  the 
carbon  and  which  serve  to  guide  the  movement  of  the 
zinc. 

This  battery  is  employed  very  extensively  in  labora- 
tories, and  presents  some  very  great  advantages:  1st, 


DEPOLARIZING-MIXTURE   BATTERIES.  223 

the  resistance  is  very  slight,  on  account  of  the  short  dis- 
tance between  the  electrodes ;  2d,  the  waste  of  the  zinc 
is  suppressed  during  the  intervals  between  experiments, 
as  it  is  withdrawn  from  the  liquid ;  3d,  polarization  is 
slackened  by  the  comparatively  large  surface  of  the  car- 
bon electrode ;  4th,  the  quantity  of  liquid  is  considerable 
on  account  of  the  spherical  form  of  the  lower  part  of  the 
bottle;  5th,  and  finally,  the  charging  and  cleaning  of 


FIG.  49. 

the  battery  is  extremely  easy,  as  there  are  but  a  single 
jar  and  a  single  liquid. 

In  spite  of  these  advantageous  dispositions,  the  battery 
gives  a  powerful  current  only  for  a  short  time,  after  which 
the  intensity  is  seen  to  diminish.  This  element  is  there- 
fore only  suitable  for  experiments  of  very  short  duration, 
such  as  are  made  in  laboratories,  or  for  surgical  opera- 
tions which  last  but  a  few  minutes. 

Sometimes  this  element  is  complicated  by  using  three 


224  TWO-LIQUID   BATTERIES. 

carbon  plates  and  two  zinc  plates;  the  surface  of  the 
electrodes  is  thus  increased,  and  the  battery  still  consists 
of  one  cell.  A  cell  of  this  kind  is  frequently  employed, 
alone  or  joined  with  others  identical,  to  excite  Rhum- 
korffs  induction-coils. 

Grenet  used  a  leaden  tube  starting  from  the  cover  and 
going  to  the  bottom  of  the  liquid.  This  tube  served  to 
introduce  air  into  the  bottle  and  to  agitate  the  liquid.  This 
idea  has  been  abandoned  in  ordinary  practice,  although  it 
possessed  great  merits. 

Although  this  be  an  element  with  no  porous  partition, 
it  is  sometimes  wrongly  called  a  single-liquid  cell ;  there 
are  in  reality  two  liquids  mixed;  viz.,  sulphuric  acid 
designed  to  act  upon  the  zinc,  and  a  mixture  of  acid  and 
bichromate  intended  to  depolarize  the  carbon. 

TROUVE'S  BATTERY. 

This  battery,  represented  by  Fig.  50,  is  a  derivative  of 
the  preceding  one.  A  certain  number  of  zinc  and  carbon 
plates  are  placed  in  a  suitable  ebonite  frame,  and  are  held 
at  short  and  equal  distances  apart,  in  such  a  manner  as  to 
be  joined  to  form  either  a  single  element  with  a  large 
surface  or  two  elements  with  a  smaller  surface  which  are 
joined  in  intensity. 

The  frame  or  box  in  which  the  plates  are  placed  is 
formed  of  an  ebonite  base  and  two  vertical  ebonite  sup- 
ports, K,  united  and  held  at  the  top  by  the  handle,  A.  The 
distances  between  the  plates  are  maintained  by  bands  of 
rubber  placed  around  the  carbons  horizontally.  In  case 
of  any  accidental  shaking  these  rubber  bands  deaden  the 
shock,  which  is  very  important  for  the  carbons,  as  their 
fragility  is  such  as  to  necessitate  great  care  to  prevent 


DEPOLARIZING-MIXTTTRE  BATTERIES. 


225 


their  being  broken.  Metallic  and  movable  clamps  are 
placed  upon  the  zinc  and  carbon  plates,  and  are  attached 
to  cross-pieces  above,  which  join  several  zinc  or  carbon 
plates  together. 

In  the  figure,  to  the  right,  in  front,  are  seen  three  car- 
bon plates  joined  together ;  this  is  the  positive  pole  of  the 


battery.  The  three  corresponding  zinc  plates  are  behind, 
joined  to  each  other  and  to  three  other  carbon  plates;  finally, 
the  last  three  zinc  plates  are  united  to  the  left,  in  front,  and 
this  forms  the  negative  pole  of  the  battery,  which  is  thus 
composed  of  two  cells  joined  in  intensity. 

The  two  cells  are  immersed  in  a  single  trough  contain- 


226  TWO-LIQUID   BATTERIES. 

ing  the  liquid,  or  rather  the  mixture.  There  is,  to  be  sure, 
a  certain  loss  of  current  by  the  liquids,  but  the  simplicity 
of  the  battery  more  than  compensates  for  the  fault  in 
question. 

A  tube,  T,  permits  the  introduction  of  air,  which  goes 
to  the  bottom  of  the  liquid,  agitates  it,  and  contributes  to 
the  depolarization.  The  battery  may  be  shaken  in  the 
liquid  by  means  of  the  handle,  which  will  produce  almost 
the  same  effect  as  the  injection  of  the  air. 

It  is  seen  from  the  preceding  that  Trouve's  arrange- 
ment presents  the  following  advantages  : 

1.  The  battery  can  be  easily  and  rapidly  dismounted,  a 
convenience  wanting  in  Grenet's  element. 

2.  The  plates,  when  dismounted,  can  be  conveniently 
washed,  which  prevents  any  slow  waste  caused  by  the  acids. 

3.  The  zinc  plates  can  be  reamalgamated,  and  when 
worn  can  be  replaced  without  the  help  of  a  special  con- 
structor. 

4.  The  clamps  washed  and  dried  may  serve  indefinitely. 
Finally,  the  battery  may'  be  so  arranged  as  to  form  two 

or  more  elements,  or  a  single  cell. 

BYKNE'S  PNEUMATIC  BATTEKY. 

Dr.  Byrne,  of  Brooklyn,  New  York,  has  invented,  upon 
the  preceding  principles,  a  battery  which  attracted  a  great 
deal  of  attention  in  1878,  and  wrhich  deserves  to  be  dwelt 
upon. 

The  positive  electrode  is  formed  of  a  plate  of  zinc  and 
placed  between  the  two  negative  electrodes,  as  in  Grenet's 
battery. 

The  double  negative  electrode  is  in  reality  a  very  thin 
plate  of  platinum.  But  Dr.  Byrne,  taking  into  account 
the  insufficient  conductibility  of  this  thin  plate,  faced  one 


DEPOLARIZING-MIXTURE   BATTERIES.  227 

side  of  it  with  a  plate  of  copper.  Moreover,  to  avoid  the 
attack  upon  the  copper,  he  coated  it  with  lead.  Thus 
the  electrode  consists  of  a  copper  plate  which  is  coated 
with  lead,  and  which  has  one  side  faced  with  a  plate  of 
platinum.  A  layer  of  varnish  protects  the  parts  of  the 
lead  which  are  not  covered  by  the  platinum. 

The  element  is  placed  in  a  large  square  ebonite  jar, 
provided  with  a  cover  of  the  same  material,  to  which  the 
two  negative  electrodes  are  attached.  Between  them  is 
suspended  the  zinc  plate,  which  may  be  immersed  in  the 
liquid  or  taken  out  when  the  battery  is  not  at  work. 

Finally,  Dr.  Byrne  affixed  to  his  battery  a  means  of 
aerating  or  agitating  the  liquid.  This  apparatus  consists 
of  a  perforated  rubber  tube,  which  is  fixed  in  the  bottom 
of  each  cell,  and  through  which  air  can  be  forced  into  the 
solution  by  means  of  a  fan  or  blower  ;  this  is  what  G-renet 
did  as  early  as  1857. 

The  intensity  of  the  current  furnished  by  this  element 
is  considerable;  it  is  especially  suited  to  medical  uses,  and 
particularly  to  cautery  purposes. 

"With  a  battery  of  10  cells  a  stout  platinum  wire,  30 
inches  long  and  1^  inches  in  diameter,  was  brought  to  a 
glowing  red  heat. 

The  advantage  of  the  injection  of  air  is  shown  by  the 
fact  that  when  air  is  being  forced  in  the  platinum  wire  is 
quickly  brought  to  a  glowing  red  heat,  and  that  on  ceas- 
ing to  inject  air  the  wire  gradually  cools  down. 

The  electro-motive  force  of  this  element  varies  but 
slightly  (from  1.73  to  1.97),  as  will  be  seen  further  on ; 
but  its  variable  resistance  (from  0.78  to  0.14  ohm)  is  al- 
ways exceedingly  small. 

This  feeble  resistance  is  the  result  of  several  circum- 
stances : 


228  TWO-LIQUID   BATTERIES. 

1.  The  nature  of  the  negative  electrode,  which  is  very 
well  combined,  and  is  superior  to  the  carbon  electrode. 

2.  The  great  coiiductibility  of  the  liquid,  which  is  very 
rich  in  sulphuric  acid. 

3.  The  high  temperature  which  is  produced  when  the 
circuit  is  closed  and  air  injected. 

AGITATION  OF  THE  LIQUID. 

We  have  already  spoken  of  the  advantage  of  agitating 
the  liquid  or  the  electrodes  of  a  battery  subject  to  polari- 
zation. The  result  is  a  freeing  of  hydrogen  bubbles 
which  diminishes  the  polarization.  It  happens  also,  some- 
times, that  precipitates  possessing  little  conduct! bility 
form  themselves  upon  the  conducting  electrodes,  and 
which  the  agitation  causes  to  fall  to  the  bottom  of  the  jar. 

This  latter  impediment  is  met  with  in  the  bichromate 
battery;  it  happens  in  certain  instances  that  there  is 
formed,  besides  the  chrome  alum,  a  yellow  precipitate 
which  partially  covers  the  carbon  and  diminishes  the  in- 
tensity of  the  battery. 

From  the  beginning,  Grenet,  to  whom  is  due  the  very 
excellent  form  of  the  element  that  we  have  made  known, 
arranged  a  tube  of  lead  descending  to  the  bottom  of  the 
liquid ;  to  this  tube  was  fastened  another  one  of  rubber, 
through  which  air  was  injected,  either  by  blowing  with 
the  mouth  or  with  a  bellows.  This  air  passed  through 
the  liquid  from  top  to  bottom,  agitated  it  and  depolarized 
the  battery :  at  least  that  is  what  it  was  believed  to  do  at 
the  time, 

Preece  has  lately  made  some  very  extensive  experiments 
upon  the  effect  of  the  injection  of  air  in  Byrne's  battery, 
which  have  given  fresh  interest  to  the  subject. 


DEPOLARIZING-MIXTURE   BATTERIES.  229 

Ladd  announced  that  by  introducing  successively  into 
the  battery  common  air,  oxygen,  and  hydrogen,  no  differ- 
ence was  observed.  Preece  confirmed  the  truth  of  this 
statement,  and  obtained  the  same  effects  by  injecting  a 
liquid  into  the  liquid.  It  is  therefore  well  established  that 
the  air  does  not  act  chemically,  but  purely  by  the  agitation 
it  produces. 

Preece  has  also  established  that  the  electro-motive  force, 
though  not  invariable,  varies  but  very  little,  the  limits  being 
1.73  and  1.97.  The  result  is  that  the  cause  of  the  change 
in  the  intensity  of  the  current  is  not  depolarization  in  the 
ordinary  sense  of  the  word. 

His  experiments  have  proved,  moreover,  that  the  inter- 
nal resistance  of  the  battery  varies  considerably  as  the 
temperature  of  the  liquid  is  increased  under  the  influence 
of  the  agitation. 

This  is.  shown  by  the  subjoined  table : 


TEMPE 
Fahr. 
80 

RATURE. 

Centig. 
26  66 

SLECTRO-MOTIVE 
FORCE. 
(Daniell=1.) 
1  73  

RESISTANCE. 
(Ohm=l.) 
0  78 

100 

37.77 

1.88  

0.61 

120 

48.88 

1.92  

035 

140 

60  00 

1.97  

0  24 

160 

71.11 

1  97  

019 

180 

82.22 

1.97  

0.17 

200 

93.33 

1.97.. 

..  0.14 

In  order  to  further  elucidate  the  question,  Preece  sub- 
mitted the  liquid  to  a  direct  experiment,  outside  of  the  bat- 
tery and  away  from  the  zinc  ;  he  employed  two  platinum 
electrodes,  as  is  almost  always  done  when  the  resistance 
of  liquids -is  to  be  ascertained,  and  he  found  the  following 
figures : 


230  TWO-LIQUID   JBATTEKIES. 

TEMPERATURE. 

Fahr.  Centig.  RESISTANCE  IN  OHMS. 

70        21.11 1.78 

90        32.22 1.50 

110        43.33 1.37 

130        54.44 1.15 

150        65.55 1.00 

170        76.66 0.79 

190        88.88 0.43 

210        99.99 0.20 

212  (boiling  point) 0.04  (variable) 

But  the  high  temperature  is  not  developed  by  the  ac- 
tion alone  of  the  acid  upon  the  bichromate  of  potash  ;  the 
zinc  must  necessarily  be  present.  One  is  led  to  the  belief 
that  the  circulation  of  the  liquid  promoted  by  the  air 
tends  continually  to  bring  fresh  acid  in  contact  with  the 
zinc  plate  and  to  disperse  the  salt  formed  at  its  surface, 
which  would  obstruct  further  action  of  the  acid. 

This  circulation  of  the  liquid  is  especially  necessary  to 
cause  a  renewal  of  the  contact  (between  the  liquid  and  the 
positive  electrode)  when  the  electrodes  are  very  near  each 
other,  as  is  the  case  in  the  batteries  of  Grenet,  of  Trouve, 
and  of  Byrne,  because  in  this  latter  instance  the  natural 
motion  of  the  liquids  is  slower  and  more  difficult. 

Other  inventors,  seeing  the  utility  of  the  agitation  in 
the  liquid,  have  sought  to  improve  upon  the  process  sug- 
gested by  Grenet.  They  have  (first  Chutaux  and  then 
Camacho)  arranged  several  elements  in  gradation,  the 
liquids  flowing  from  one  to  the  other  and  thereby  pro- 
ducing a  renewal  of  the  active  fluid  at  the  contact  with 
the  electrodes. 


DEPOLAKIZING-MIXTURE   BATTERIES.  231 


CAMACHO'S   BATTERY. 

We  have  said  above  that  Chutaux  sought  to  produce 
the  agitation  of  the  liquids  which  is  so  advantageous  in 


FIG.  51. 


the  bichromate-of -potash  battery,  by  placing  the  cells  one 
above  the  other  and  causing  the  liquid  to  pass  succes- 


232  TWO-LIQUID   BATTERIES. 

sively  in  two  or  three  cells.  This  disposition  appears  to 
us  very  cumbersome,  and  we  prefer  that  of  Camacho, 
represented  by  Fig.  51. 

The  jars  are  placed  in  gradation  upon  steps ;  the  liquid 
falls  from  a  special  reservoir  into  the  porous  jar  of  the 
top  cell,  whence  it  is  carried  by  means  of  a  siphon  into 
the  succeeding  one,  and  so  on. 

The  negative  electrode  consists  of  a  small  bar  of  carbon 
and  a  considerable  mass  of  crushed  gas-retort  carbon, 
which  fills  the  porous  jar ;  the  enormous  surface  of  this 
electrode  renders  polarization  very  slow. 

We  have  recommended  this  disposition  for  all  batteries 
subject  to  polarization,  that  is  for  those  which  have  not 
an  absolutely  efficient  depolarizing  agent.  In  this  battery 
it  is  very  advantageously  applied.  Grangain  has  published 
tables  of  comparison,  which  show  the  influence  of  crushed 
carbon  placed  around  the  principal  plate. 

DELAUEIEE'S  BATTERY. 

This  is  a  modification  of  the  bichromate-of-potash 
battery.  It  has  in  the  outer  jar  a  zinc  electrode  which 
surrounds  the  porous  jar,  in  which  is  a  carbon  electrode. 
When  the  battery  is  charged,  pure  water  is  put  with  the 
zinc,  and  with  the  carbon  a  liquid  composed  of  water, 
bichromate  of  potash,  sulphate  of  soda,  sulphate  of  iron, 
and  sulphuric  acid. 

At  first  starting  the  resistance  is  considerable  on  account 
of  the  pure  water  in  the  outer  jar ;  but  a  certain  quantity 
of  the  compound  liquid  soon  passes  through  the  pores  of 
the  diaphragm  and  the  resistance  of  the  element  diminishes 
about  one  half. 

It   is   difficult   to   ascertain    precisely   what   chemical 


DEPOLAKIZING-MIXTTJKE   BATTETCIES.  233 

actions  take  place  between  these  numerous  compounds, 
either  while  the  circuit  is  open  or  closed.  However, 
Delaurier's  battery  is  employed  by  many,  and  especially 
for  depositing  silver,  for  depositing  nickel,  gilding,  etc. 

The  advantages  of  this  battery  are  mostly  attributed  to 
the  proportions  of  its  different  parts.  The  porous  jar  is 
comparatively  large  and  contains  two  carbon  plates  instead 
of  one,  which  diminishes  the  internal  resistance. 


PAET  III, 
VARIOUS  BATTERIES. 


DEY    PILES. 

WE  will  briefly  describe  those  galvanic  batteries  called 
dry  piles,  in  which  the  liquid  is  replaced  by  a  slightly 
moistened  or  oily  substance. 

In  reality,  these  batteries  are  not  dry,  and  cease  to  work 
when  they  are  thoroughly  dried.  In  the  beginning,  cells 
were  formed  of  two  thin  plates  of  copper  and  of  zinc, 
having  between  them  a  sheet  of  paper  saturated  with  oil 
or  salt  water  and  nearly  dry. 

In  1812  Zamboni  suggested  a  more  original  disposition, 
which  has  been  but  slightly  modified,  and  which  is  con- 
structed as  follows : 

A  sheet  of  paper  is  turned  upon  one  side,  and  upon  the 
other  side  is  spread  with  a  small  brush  a  thin  layer  of 
peroxide  of  manganese  thinned  with  milk  or  with  gummy 
water,  or  even  with  common  paste ;  this  is  left  to  dry, 
and  then,  placing  a  certain  number  of  these  sheets  one 
upon  another,  small  discs  about  \\  in.  in  diameter  are  cut 
out  by  means  of  a  punch ;  the  discs  are  then  placed  one 
upon  another  in  regular  order.  To  render  this  pile  of 
discs  solid,  the  latter  are  placed  in  a  glass  tube  well  var- 
nished on  the  inside ;  they  are  pressed  down  as  tightly  as 
possible,  in  order  to  insure  good  contact.  At  both  'ends 


236  VARIOUS   BATTERIES. 

there  are  metallic  plates  wliich  represent  the  poles  of  the 
battery.  These  metallic  plates  are  a  little  larger  in  diam- 
eter than  the  discs  of  the  battery  and  are  pierced  with 
several  holes,  through  wliich  silk  cords  are  passed  which 
hold  the  compressed  column  and  even  dispense  with  the 
glass  tube  of  which  we  have  spoken. 

Great  care  must  be  taken,  especially  when  the  glass 
tube  is  not  used,  to  exclude  the  air,  which  may  be  done 
by  covering  the  pile  with  gum  lac  or  with  sulphur ;  other- 
wise losses  would  be  sustained  on  account  of  the  humidity 
of  the  air,  and  the  effects  of  the  battery  would  be  greatly 
lessened. 

Electric  sparks  can  be  produced  with  these  batteries,  as 
their  electro-motive  force  is  considerable  on  account  of 
the  large  number  of  elements  wliich  enter  into  their 
composition. 

The  internal  resistance  of  these  batteries  is  enormous, 
as  is  easily  understood.  This  explains  why  a  most  sensi- 
tive galvanometer  is  needed  to  detect  any  current. 

It  is  easy  to  comprehend  how  dry  piles  recover  but 
slowly  their  charge,  after  having  been  discharged,  and 
how  they  do  not  receive  their  maximum  charge  in  a  damp 
atmosphere. 

Zamboni's  batteries  do  not  last  forever;  it  has  been 
proved  that  after  a  few  years  they  lose  all  their  force. 
In  their  last  stages  of  weakness,  a  portion  of  their  energy 
may  be  restored  by  exposing  them  to  an  intense  heat. 
It  is  probable  that  the  chemical  actions  are  thus  accel- 
erated. 

The  chemical  reaction  which  takes  place  in  each  element 
is  very  simple ;  the  peroxide  of  manganese  is  decomposed 
and.  the  tin  is  oxidized  at  its  expense.  It  is  to  be  noted 
that  the  bioxide  plays  the  part  of  both  conducting  electrode 


VARIOUS   BATTERIES.  237 

and  of  active  substance.  The  paper  acts  as  simple  con- 
ductor, which  property  it  owes  to  the  humidity  it  con- 
tains. When  this  humidity  disappears,  the  battery  no 
longer  produces  any  electricity,  and  it  is  only  necessary 
to  expose  it  to  damp  air  in  order  that  it  may  recover  its 
electro-motive  properties.  Experiments  show  that  dry 
piles  possess  all  the  properties  of  ordinary  batteries. 

Dry  piles  used  to  be  employed  to  turn  small  apparatus 
based  upon  the  attraction  and  repulsion  of  electrified 
bodies.  Perpetual  motion  was  thought  to  have  been 
secured,  but  after  a  few  years  these  apparatus  stopped, 
proving  once  more  the  folly  of  such  a  research  after  the 
impossible.  These  scientific  playthings  have  now  gone  out 
of  fashion ;  no  more  are  constructed,  but  they  are  found 
described  and  illustrated  in  nearly  all  works  upon  physics. 

To-day  dry  piles  are  only  used  in  connection  with 
electroscopes,  notably  with  that  of  Bohnenberger,  the 
description  of  which  is  found  in  most  works  treating  of 
the  subject. 

IDENTICAL  ELECTKODE  BATTEKIES. 

Hitherto  in  batteries  we  have  always  met  with  two 
distinct  electrodes  immersed  in  one  or  two  liquids. 

We  desire  to  show  that  batteries  may  be  composed 
which  contain  identical  electrodes,  provided  these  elec- 
trodes be  immersed  in  two  different  liquids.  The  direc- 
tion of  the  current  will  be  determined  because  one  of  the 
liquids  will  attack  its  electrode  more  actively  and  the  other 
will  attack  its  electrode  less  actively  or  not  at  all. 

We  will  give  a  very  simple  example.  In  a  jar  put  a 
saturated  solution  of  sulphate  of  copper,  and  on  top  of  this 
some  acidulated  water,  or  salt  water,  or  pure  water.  Now 


238  VARIOUS   BATTERIES. 

if  a  copper  plate  be  placed  on  end  in  this  liquid,  it  will  be 
attacked  at  the  top  and  become  charged  with  copper  at 
the  bottom.  It  is  plain  that  we  have  there  an  element  of 
copper,  acidulated  water,  sulphate  of  copper,  and  copper. 

This  experiment  furnishes  the  explanation  of  how  a 
drop  of  sulphate  of  copper  thrown  upon  copper  will  pro- 
dace  an  attack,  the  same  as  a  drop  of  nitrate  of  silver  upon 
a  silver  plate.  It  happens  that,  by  difference  of  specific 
gravity,  the  more  saturated  solution  falls  to  the  bottom 
and  the  less  charged  solution  rises  to  the  top;  conse- 
quently a  current  is  produced  which  transfers  the  metal 
from  one  point  to  another.  In  order  to  have  no  action 
at  all,  the  composition  of  the  liquid  ought  to  be  the  same 
throughout. 

We  thought  it  better  to  note  these  observations  to  show 
the  reader  that  various  phenomena  not  apparently  electric 
can  in  reality  only  be  explained  by  electro-chemistry. 

UNATTACKED  ELECTKODES  IN  BATTEEIES. 

In  all  the  batteries  hitherto  described  we  have  found  a 
metallic  generating  electrode.  This  electrode  is  dissolved 
in  the  liquid  in  which  it  is  immersed,  and  this  action  pro- 
duces a  current.  But  the  actions  between  liquids  can 
also  produce  electricity. 

If  in  a  vessel  divided  into  two  compartments  by  a 
porous  partition  acid  is  put  in  one  division  and  an  alka- 
line solution  in  the  other,  there  will  be  a  reciprocal  reac- 
tion in  the  pores  of  the  diaphragm  and  the  formation  of 
a  salt ;  if  two  platinum  plates  be  immersed  in  the  liquids 
a  current  will  be  made  manifest  in  a  wire  conductor 
uniting  the  two  plates.  The  positive  pole  of  this  element 
will  correspond  to  the  acid.  Nothing  would  be  changed 


VAEIOUS   BATTERIES.  239 

if,  instead  of  two  platinum  plates  immersed  in  the  two 
compartments,  there  were  one  of  platinum  and  one  of 
gold.  Neither  of  them  are  attacked,  both  are  conducting 
electrodes,  and  there  is  in  reality  no  generating  electrode. 
"We  will  not  insist  upon  these  voltaic  contrivances 
which  have  as  yet  received  no  application.  It  should  be 
noticed,  however,  that  they  generally  polarize  like 
ordinary  batteries.  A  single  one  has  been  invented 
which  does  not  polarize,  and  which  should  be  noted  in 
the  enumeration  that  we  have  undertaken. 

BECQUEKEL'S  OXYGEN-GAS  BATTEKY. 

This  apparatus  is  composed  as  follows :  A  glass  tube 
closed  at  the  bottom  by  a  porous  partition  is  placed  in  a 
flask  containing  nitric  acid  ;  potash  is  poured  in  the  glass 
tube,  and  in  each  liquid  is  placed  a  bar  of  platinum  to 
which  a  conductor  is  attached.  "When  the  circuit  is 
closed  by  bringing  the  two  connections  in  contact  with 
each  other,  a  lively  action  takes  place,  the  acid  and  the 
base  combine.  But  this  simple  reaction  does  not  take 
place  alone ;  the  current  thus  produced  decomposes  the 
surrounding  water,  the  hydrogen  goes  to  the  nitric  acid, 
which  it  reduces,  and  is  not  given  off  upon  the  electrode ; 
consequently  there  is  no  polarization.  The  oxygen  goes 
to  the  potash,  remaining  free,  and  surrounds  the  plati- 
num plate. 

This  battery  is  remarkable  as  being  the  only  one  in 
which  oxygen  is  evolved,  the  contrary  from  all  other 
batteries  in  which  hydrogen  is  evolved  (except,  of  course, 
totally  depolarized  batteries). 

It  moreover  possesses  a  great  historical  interest,  be- 
cause it  is  the  first  battery  furnishing  a  constant  current 


240  VARIOUS   BATTEEIES. 

that  was  constructed ;  it  is  in  this  element  that  were  first 
employed  two  liquids  and  a  porous,  diaphragm. 

COKE-CONSUMING  BATTEEY. 

Throughout  this  work  we  have  shown  that  the  com- 
bustion or  dissolving  of  zinc  is  the  principal  and  almost 
only  means  employed  to  produce  voltaic  electricity. 
Thus,  each  equivalent  of  electricity  costs,  at  the  mini- 
mum, one  equivalent  of  zinc  plus  an  equivalent  of  one 
or  two  other  substances,  and  it  is  for  that  reason  that 
electricity  is  so  expensive. 

It  might  be  reasonably  inquired  whether  the  combus- 
tion of  common  coal  could  not  be  utilized  for  the  produc- 
tion of  electric  currents. 

Magneto-electrical  machines,  which  furnish  a  continu- 
ous current,  and  of  which  the  Gramme  machine  is  the 
model,  present  a  solution  of  this  problem.  When  a 
Gramme  machine  is  put  into  motion  by  a  steam  motor, 
there  is  seen  a  transformation  into  electricity  of  the  heat 
produced  by  the  combustion  of  the  coal  in  the  furnace  of 
the  motor.  That  is  an  indirect  solution,  for  the  heat  is 
first  transformed  into  motive  force,  which  is  in  turn 
transformed  into  electricity.;  but  it  is  a  very  good  solu- 
tion, and  is  to-day  confirmed  by  practice.  If  the  elec- 
tricity produced  by  Gramme  machines  cost  but  little,  it 
is  because  it  is  produced  by  the  combustion  of  coal,  which 
is  as  yet  the  most  advantageous  source  of  energy  discov- 
ered— an  energy  which  presents  itself  in  the  form  of 
heat,  of  chemical  energy,  of  movement,  or  of  electricity, 
and  which  may  be  transformed  into  one  or  the  other  of 
these  four  powers. 

It  is  very  probable  that  a  direct  transformation  into 


VARIOUS   BATTEEIES.  241 

electricity  of  the  heat  produced  by  the  combustion  of 
coal  may  be  obtained.  Mr.  Jablochkoff  has  already  in- 
vented a  battery  cell  which  fulfils  the  above  conditions. 

The  liquid  of  this  cell  is  melted  nitrate  of  potash  or 
nitrate  of  soda ;  one  electrode  is  of  coke,  and  the  other 
of  platinum,  or  even  of  cast-iron.  The  coke  is  burned  at 
the  expense  of  the  oxygen  of  the  nitrate,  and  produces 
torrents  of  carbonic  acid;  the  cast-iron  remains  unat- 
tacked. 

The  coke  is  therefore  the  positive  electrode,  and  the 
cast-iron  the  negative.  It  is  the  contrary  of  that  which 
would  take  place  in  a  battery  with  an  ordinary  liquid, 
acid,  or  salt  dissolved  in  water. 

The  nitrate  should  be  previously  melted,  but  as  soon  as 
the  action  begins  the  salt  remains  liquid  on  account  of 
the  great  heat  produced  by  the  combinations  which  take 
place ;  and  if  the  element  be  left  to  itself  it  suffices,  to 
put  it  in  action,  to  bring  the  end  of  the  coke  to  a  glowing 
red  heat,  and  then  to  press  it  against  the  surface  of  the 
salt ;  the  chemical  action  begins  immediately,  and  by  the 
heat  it  produces  the  melting  of  the  nitrate,  and  soon  the 
element  is  reproduced. 

It  might  be  found  that  such  a  battery  cell  presents 
nothing  practical  in  its  actual  form,  and  we  do  not  hesi- 
tate to  express  that  opinion,  but  we  believe  that  it  points 
out  a  new  way  in  which  much  progress  might  be  made 
if  the  attention  of  physicists  were  turned  in  that  direc- 
tion. Yolta's  battery  itself  when  invented  was  a  purely 
scientific  novelty,  and  it  was  far  from  being  regarded  as 
an  object  of  any  practical  utility. 

Mr.  JablochkofFs  experiment  will  doubtless  call  forth 
many  commentaries.  This  is  not  the  place  for  any  re- 
marks upon  the  subject.  We  only  wished,  in  mention- 


242  VAEIOUS   BATTEKIES. 

ing  tliis  battery  cell,  to  show  our  readers  that  beyond  the 
already  explored  horizons  there  remain  other  worlds  to 
discover  and  virgin  lands  to  cultivate. 

GAS  BATTEEIES. 

"We  have  explained  how  a  voltameter,  in  which  oxygen 
and  hydrogen  were  evolved,  could  become  a  source  of 
electricity.  To  show  this,  it  is  only  necessary  to  attach 
the  wires  of  a  galvanometer  to  the  terminals  of  a  vol- 
tameter thus  charged. 

If  the  electrodes  of  the  voltameter  are  immersed  partly 
in  the  acidulated  water  and  partly  in  the  previously 
evolved  gases,  the  voltameter  may  furnish  a  current 
during  a  considerable  length  of  time;  the  oxygen  and 
hydrogen  recombinc  through  the  liquid,  and  the  current 
resulting  from  this  combination  lasts  as  long  as  there  i& 
any  gas  in  contact  with  one  or  the  other  of  the  elec- 
trodes. 

Under  these  circumstances,  a  voltameter  becomes  in 
reality  a  gas  battery.  When  the  gases  are  consumed 
they  can  be  replaced,  and  the  action  of  the  battery  pro- 
longed, just  as  acids  or  salts  are  renewed  in  ordinary 
batteries. 

Grove,  to  whom  is  due  the  invention  of  these  interest- 
ing contrivances,  has  given  to  them  many  and  various 
forms.  He  has  also  substituted  for  the  oxygen  and  the 
hydrogen  other  gases,  such  as  chlorine,  protoxide  of  car- 
bon, bioxide  of  nitrogen,  olefiant  gas,  and  has  found  bat- 
teries analogous  to  the  first  one.  He  has  discovered  that 
certain  gases  when  taken  together  produce  no  electric 
current ;  viz.,  nitrogen  and  oxygen,  nitrogen  and  hydro- 
gen, protoxide  of  nitrogen  and  oxygen. 


YAEIOUS   BATTERIES.  243 

A  certain  number  of  cells,  such  as  we  have  described, 
may  be  joined  in  intensity,  and  it  will  be  seen  that  they 
possess  the  same  general  properties  as  ordinary  batteries. 

Gaugain  has  established  the  fact  that  gas  batteries  do 
not  act  except  by  dissolved  gases ;  so  that  their  force  be- 
comes less  as  the  solution  weakens,  just  as  in  sulphate-of- 
mercury  and  sulphate-of-lead  cells. 

It  is  moreover  probable  that,  in  addition  to  this  special 
weakening,  gas  batteries  are  liable  to  polarize  like  the 
others,  especially  when  there  are  several  elements  in  the 
circuit. 

Batteries  in  which  only  one  of  the  active  bodies  is 
gaseous,  while  the  other  is  liquid,  have  also  been  dis- 
covered. 

Thus  Grove  has  been  able  to  obtain  a  current  by  caus- 
ing oxygen  to  act  upon  sulphate  of  protoxide  of  iron, 
which  is  subject  to  oxidation  and  is  transformed  into 
sulphate  of  peroxide,  or  by  causing  hydrogen  to  act  upon 
nitric  acid,  which  decomposes  and  gives  off  oxygen. 

Ed.  Becquerel  caused  hydrogen  to  act  upon  chloride  of 
gold  in  the  presence  of  platinum. 

Two  or  single  gas  batteries  can  receive  no  application ; 
the  great  interest  they  possess  is  simply  theoretical. 

SECOND AEY  BATTEEIES. 

We  have  already  said  that  a  voltameter  submitted  to 
the  influence  of  an  electric  current  for  a  moment  be- 
comes capable  of  furnishing  a  current  contrary  to  the  ex- 
citing current.  This  capital  fact  has  enabled  us  to  show, 
under  one  of  its  plainest  forms,  the  phenomenon  of  the 
polarization  of  electrodes. 

The  current  thus  furnished  by  the  voltameter  is  a  sec- 


244  VARIOUS   BATTEEIES. 

ondary  current,  and  the  apparatus  becomes  a  secondary 
element.  The  current  may  be  said  to  have  been  fur- 
nished by  the  battery,  and  returned  by  the  secondary 
element. 

The  study  of  this  question  dates  from  the  beginning 
of  the  present  century — Gautlierot  in  1801,  and  soon 
after  Hitter  called  attention  to  it.  Hitter  has  shown 
that  secondary  elements  may  be  produced  under  other 
forms  than  that  of  the  voltameter;  two  electrodes  of 
platinum,  of  carbon,  of  copper,  or  indeed  of  more  easily 
oxidized  metals,  placed  in  a  conducting  liquid,  suffice  to 
constitute  a  secondary  element. 

A  column  battery  formed  of  a  succession  of  discs  of 
copper  and  cloth  moistened  with  sulphate  of  potash  con- 
stitutes a  secondary  battery. 

Pursuing  the  general  idea  with  which  this  work  has 
been  written,  we  can,  in  conclusion,  do  no  better  than  to 
study  in  detail  secondary  batteries,  which  present  an 
application  of  the  polarization  of  electrodes. 

To  make  the  subject  clear,  let  us  consider  a  secondary 
battery  formed  of  two  platinum  plates  immersed  in  acidu- 
lated water. 

The  most  feeble  current  suffices  to  polarize  these  elec- 
trodes, as  can  be  shown  by  carefully  observing  the  sec- 
ondary current.  It  is  not  necessary  that  the  exciting 
current  should  have  a  tension  sufficiently  great  to  decom- 
pose water ;  one  of  Daniell's  elements,  or  even  a  more 
feeble  one,  can  polarize  the  secondary  element. 

When  the  cell  is  polarized  by  a  more  energetic  current, 
the  secondary  current  also  increases  in  energy,  but  it  is 
clear  that  the  electro-motive  force  of  the  second  can  never 
be  superior  to  that  of  the  first. 

If  in  a  circuit  are  placed  an  ordinary  cell,  a  galvanome- 


VAEIOUS   BATTEKIES. 


245 


ter,  and  a  secondary  cell,  the  following  facts  are  ob- 
served :  at  first  the  current  of  the  polarizing  cell  passes 
with  great  energy,  as  the  galvanometer  shows,  then  it 
gradually  diminishes  on  account  of  the  increasing  polari- 
zation of  the  secondary  cell. 

If  the  polarizing  current  is  not  sufficient  to  decompose 
water — if,  for  instance,  it  is  furnished  by  one  of  Daniell's 
cells — it  happens  that  the  secondary  current  eounterbal- 


FIG.  52. 

ances  the  principal  current,  as  shown  by  the  galvanome- 
ter, which  marks  no  deflection. 

If  the  principal  current  is  sufficient  to  decompose 
water,  the  above  equality  is  never  reached,  and  the  free- 
ing of  gases  corresponds  indefinitely  to  a  circulation  of 
the  current  made  manifest  by  the  galvanometer. 

If,  instead  of  a  single  secondary  element,  several  are 
placed  in  the  circuit,  polarization  will  be  divided  between 
them  ;  each  one  taken  separately  will  furnish  a  secondary 
current  after  being  a  moment  under  the  influence  of  the 
principal  current,  but  the  sum  of  the  electro-motive  forces 


246 


VARIOUS   BATTERIES. 


cf  these  secondary  currents  can  never  become  superior  to 
that  of  the  polarizing  current. 

But  if  these  secondary  cells  be  charged  separately  and 
then  joined  in  intensity,  the  total  current  might  have  a 


FIG.  53. 

considerable  energy  and  be  superior  to  that  of  the  princi- 
pal current  by  which  they  have  been  successively  ex- 
cited. 


VARIOUS   BATTERIES.  247 

All  this  will  be  made  clearer  by  the  following  detailed 
study  of  secondary  cells  having  electrodes  of  lead. 

As  early  as  1859  Mr.  Plante  showed  that  lead  was  the 
most  favorable  metal  for  use  in  secondary  batteries,  and 
he  has  since  that  time-  accumulated  many  proofs  of  this 
superiority.  Figs.  52  and  53  show  the  element  as  con- 
structed to-day.  In  a  tall  vessel  made  of  glass,  of  rubber, 
or  of  ebonite  are  placed  two  sheets  of  lead  rolled  to- 
gether parallel  to  each  other,  and  kept  apart  by  two 
strips  of  rubber  rolled  with  them ;  these  two  sheets  are 
immersed  in  a  solution  containing  one  tenth  of  sulphuric 
acid.  The  vessel  is  closed  by  a  sealed  stopper  in  which 
there  is  a  hole  through  which  the  liquid  is  introduced 
and  extracted,  and  through  which  the  gases  evolved  dur- 
ing the  charging  may  pass  off.  The  apparatus  is  capped 
by  an  ebonite  cover  furnished  with  two  clamp  screws 
which  communicate  with  the  two  electrodes ;  there  are 
also  two  clamps,  which  hold  metallic  wires  to  be  heated 
and  melted  by  the  secondary  current. 

To  charge  this  secondary  element  to  its  maximum,  two  of 
Bunsen's  cells  or  three  of  Daniell's  must  be  used.  During 
the  charging,  one  of  the  electrodes  becomes  oxidized,  a 
brownish  layer  of  peroxide  of  lead  is  soon  seen,  and  the 
metallic  aspect  completely  disappears  ;  the  other  electrode 
only  changes  in  appearance,  its  surface  becoming  covered 
with  a  grayish  matter. 

"When  it  is  charged  to  its  maximum — that  is,  when  oxy- 
gen begins  to  free  itself  from  the  brown  electrode — it  is 
well  to  separate  the  secondary  cell  from  the  active  battery, 
as  the  polarizing  current  is  no  longer  useful  and  is  wasted. 

The  secondary  element  thus  charged  and  left  to  itself 
can  preserve  a  part  of  its  charge  several  days,  and  at  the 
end  of  a  week  it  is  still  far  from  being  exhausted. 


248  VARIOUS   BATTERIES. 

The  secondary  cell  when  charged  to  its  maximum  has 
an  electro-motive  force  equal  to  one  and  a  half  that  of 
Bunsen's  cell ;  it  can  bring  to  a  glowing  red  heat  a  platinum 
wire  large  or  small  according  to  the  dimensions  of 
the  cell,  or,  better,  according  to  the  size  of  its  electrodes. 
It  can  be  easily  understood,  indeed,  that  the  quantity  of 
electricity  furnished  by  the  apparatus  is  in  proportion  to 
the  extent  of  surface  of  the  lead  submitted  to  the  action 
of  the  polarizing  current  and  covered  with  an  active  elec- 
tro-chemical deposit. 

It  should  be  noted  that  the  peculiar  form  of  the  elec- 
trodes offers  a  large  surface  and  a  small  resistance  under 
a  small  volume  ;  so  that  one  of  Plante's  secondary  cells  is 
equal  to  an  active  or  ordinary  cell  of  extraordinary  dimen- 
sions ;  the  small  model  has  a  surface  of  eight  square 
decimetres,  the  large  one  a  surface  of  four  square  deci- 
metres. 

The  current  furnished  by  a  secondary  element  can 
produce  chemical  decompositions,  act  upon  an  electro- 
magnet, etc. ;  but  if  its  intensity  be  measured  in  one  way 
or  another,  with  a  galvanometer  for  instance,  it  is  seen  to 
diminish  from  the  maximum  of  which  we  have  spoken 
above.  This  decrease  is  very  slow  if  the  circuit  offers  a 
great  resistance,  and  if,  as  a  consequence,  there  is  a  very 
small  flow  of  electricity  ;  it  is  on  the  contrary  very  rapid 
if  the  circuit  offers  but  a  slight  resistance,  because  -  the 
electricity  flows  in  a  large  quantity. 

A  very  curious  and  interesting  fact  is  noticed  during 
the  discharge  of  the  cell ;  it  is  apparently  completely  dis- 
charged, but  if  the  circuit  be  left  open  several  minutes, 
it  has  been  ascertained  that  it  recovers  a  certain  energy 
and  that  it  can  still  furnish  a  certain  quantity  of  elec- 
tricity. 


VARIOUS   BATTERIES.  249 

The  battery  thus  delivered  of  its  first  residue  and  left 
to  itself  for  some  time  will  furnish  a  second  residue,  less, 
of  course,  than  the  first.  And  this  is  not  the  last  one,  for 
several  more  can  be  obtained.  Mr.  Plante  has  very 
clearly  explained  this  peculiarity.  The  se  condary  element, 
when  it  becomes  active,  discharges  itself  and  at  the  same 
time  polarizes,  as  all  single-liquid  batteries.  This  polari- 
zation attains  in  a  certain  time  a  force  almost  equal  to 
that  of  the  already  weakened  secondary  element,  and  the 
action  ceases  or  is  reduced  to  very  little.  If  the  battery 
then  be  left  to  rest,  it  depolarizes  as  do  all  single-liquid 
batteries  polarized  by  their  own  action.  As  soon  as  the 
battery  is  depolarized  it  is  again  ready  to  furnish  a  cur- 
rent, but  during  this  new  discharge  it  again  polarizes, 
and  so  on. 

If  we  consider  the  secondary  cell  as  completely  or 
almost  completely  discharged,  it  may  be  recharged  with 
two  of  Bunsen's  elements,  as  in  the  first  instance ;  but  it 
is  well  to  note  that  the  more  immediately  after  the  dis- 
charge the  new  charge  be  given,  the  more  rapidly  it  may 
be  given. 

Moreover,  the  greater  number  of  times  a  secondary 
element  is  charged  and  discharged,  the  better  it  is.  In 
the  beginning,  when  it  is  nearly  new,  there  is  an  advan- 
tage in  polarizing  the  electrodes,  first  in  one  direction 
and  then  in  the  other,  and  in  reversing  several  times  the 
direction  of  the  charge  ;  but  when  the  element  is  formed, 
great  care  must  be  taken  to  always  charge  it  in  the  same 
direction.  If  this  precaution  be  neglected  it -will  take  a 
much  longer  time  to  charge  it,  for  the  oxide  of  lead,  which 
may  still  remain  upon  one  of  the  electrodes,  must  be  re- 
duced and  the  previously  negative  plate  oxidized.  But 
after  this  operation  the  secondary  cell  will  have  recovered 


250 


VARIOUS   BATTERIES. 


FIG.  54. 


all  its  qualities :  it  may  indeed  be  said  to  have  gained 
some. 

Fig.  54  shows  a  peculiar  form  given  to  the  secondary 
element  by  Mr.  Plante,  and  which  he  has  called  Saturn's 
tinder-box.  At  the  top  are  seen  two  clamps  which  hold  a 

platinum  wire  stretched 
between  them ;  each  time 
that,  by  pressing  with  the 
finger,  the  two  springs  at 
the  bottom  are  brought 
into  contact  the  battery 
sends  a  current  through 
the  platinum  wire,  which 
is  thereby  brought  to  a 
glowing  red  heat,  whence 
follows  an  almost  instan- 
taneous lighting  of  the 

candle.  With  one  of  these  contrivances  the  candle  may 
be  lighted  one  hundred  times,  and  it  is  only  after  these 
frequent  lightings  that  it  has  to  be  recharged  with  three 
of  DanielPs  cells.  That  is  a  means 'of  obtaining  fire  and 
a  very  economical  means  too,  for  the  secondary  element 
spends  nothing  and  the  charging  battery  consumes  but  a 
few  grammes  of  sulphate  of  copper  for  a  prolonged 
working  of  the  tinder-box. 

This  same  apparatus  can  be  used  to  touch  off  mines 
either  in  civil  or  military  service  ;  the  experiment  shows 
that  with  fine  platinum-wire  fuses  (^-J-g-  of  an  inch) 
combustion  may  be  obtained  through  a  copper  wire  1000 
yards  long. 

With  a  contrivance  of  this  kind  surgeons  may  cauterize 
a  wound,  and  it  has  frequently  been  applied  in  that 
way.  A  secondary  element  is  much  more  easily  trans- 


VARIOUS   BATTERIES. 


251 


ported  into  a  hospital  or  to  the  house  of  a  sick  person 
than  active  cells  which  it  may  replace. 

Finally,  secondary  cells  can  be  joined  in  quantity  or  in 
intensity  and  constitute  batteries  capable  of  producing  all 
the  effects  of  the  most  powerful  ordinary  batteries. 
Fig.  55  represents  the  secondary  battery  as  disposed  by 
Mr.  Plant& 

The  number  and  dimensions  of  the  cells  can  be  varied 
according  to  the  tension  and  quantity  desired.  Here  there 


FIG.  55. 

are  twenty  elements  arranged  in  two  rows.  At  the  top 
there  is  a  very  conveniently  disposed  commutator,  which, 
in  one  position,  joins  the  cells  in  quantity;  in  another 
position,  at  right  angles  with  the  first,  it  joins  them  in 
intensity.  In  the  first  position  all  the  outer  electrodes 
are  joined  to  one  metallic  strip,  and  all  the  inner  elec- 
trodes to  another  metallic  strip,  so  that  the  whole  arrange- 
ment represents  a  single  cell  with  a  large  surface.  It  is 
in  this  condition  that  the  charge  is  made ;  two  of  Bun- 
sen's  cells  are  sufficient,  and  they  complete  the  charge  in 


252  VAEIOUS   BATTERIES. 

a  longer  or  shorter  time,  according  to  the  dimensions  of 
the  cells  and  to  the  extent  of  the  surface  of  the  lead  to 
be  polarized.  In  the  second  position  the  outer  electrode 
of  eadi  cell  is  put  into  communication  with  the  inner 
one  of  the  following  cell,  and  the  apparatus  becomes  a 
real  battery  of  twenty  cells.  It  is  in  this  condition  that 
the  battery  is  discharged,  and  it  is  equal,  at  first  starting, 
to  30  of  Bunsen's  very  large  cells. 

As  the  battery  is  being  discharged  the  tension  dimin- 
ishes, as  we  explained  when  speaking  of  the  single  sec- 
ondary element.  If  it  takes  one  minute  to  charge  the 
battery  of  secondary  cells  in  quantity,  it  cannot  be  expected 
that  the  discharge  of  the  cells  in  intensity  will  furnish  the 
same  effects  as  30  of  Bunsen's  of  the  same  size  during  a 
longer  period  than  four  seconds,  for  the  apparatus  fur- 
nishes no  electricity  and  can  only  transform  that  which 
has  been  given  to  it.  Mr.  Plarite  has  made  some  exact 
experiments  in  this  direction,  and  has  found  that  in  this 
transformation  about  one  tenth  is  lost,  or,  in  other  words, 
the  machine  returns  nine  tenths  of  that  which  was  given 
to  it. 

It  is  clearly  seen  that  the  secondary  battery  can  only 
produce  effects  of  very  short  duration,  but  in  most  cases 
this  is  all  that  is  neccesary. 

If,  for  instance,  a  large  number  of  mines  are  to  be 
simultaneously  exploded  by  means  of  fuses  of  fine  wire,  it 
may  be  done  by  placing  all  the  fuses  in  divided  circuits 
and  by  causing  the  current  of  the  secondary  battery  to 
pass  through  them  all  at  once.  This  manner  of  preceding 
is  very  economical,  and  it  is  certainly  less  laborious  and 
costly  to  mount  two  of  Bunsen's  cells  and  to  charge  a 
Decondary  battery  than  to  charge  20  or  30  of  Bunsen's 
elements,  especially  when  the  battery  is  only  worked  a 
few  seconds  and  only  four  or  five  times  during  a  day. 


TABLESc 


253 


I.  ELECTRIC    CONDUCTING   POWER    OF    SOLIDS. 
(Ed.  Becquerel. — Annales  de  CMmie  et  de  Physique,  1846.) 


SUBSTANCES. 

Metal 
(hard  drawn). 

Metal 
(annealed). 

Silver,  pure  (reduced  from  the  chloride)  
Copper,  pure  electro-chemical  

93.448 
89.048 

100.000 
91.439 

Gold,  pure    ... 

64  385 

65.458 

Cadmium 

24  574 

Zinc  

24.164 

Tin 

13  656 

Palladium  

13.977 

Iron  

12  124 

12.246 

Lead 

8  245 

Platinum  

8.042 

8.147 

Mercury  at  14°  centi01 

1  8017 

SUBSTANCES. 

Conduc 
0°  Centig. 

tivity  at 
100°  Centig. 

Coefficient 
for 
1°  Centig. 

Silver  annealed 

100. 
91.517 
64.960 
24.579 
24.063 
14.014 
12.350 
8.277 
7.933 
1.7387 

71.316 
64.919 
48.489 
17.506 
17.596 
8.657 
8.387 
5.761 
6.688 
1.5749 

0.004022 
0.004097 
0.003397 
0.004040 
0.003675 
0.006188 
0.004726 
0.004349 
0.001861 
0.001040 

Copper  

Gold 

Cadmium  

Zinc  

Tin 

Iron,  annealed  

Lead 

Platinum,  annealed  

Mercury,  distilled  ...  . 

254 


TABLES. 


II.    SPECIFIC    RESISTANCES   DETERMINED 
MATTHIESEN. 


le  taken  from  Fleeming  Jenkin.) 


BY 


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«w  t-i  fcX) 

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O+i  g 

NAMES  OF  METALS. 

®~S  9^ 

.0  £3  ti 

CD-w'S 

0  O  S) 

o  g'-g'g 

*°"£:3-2 

*  S'23  s 

0  °.S 

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nil 

In  <K  <D  § 

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isi 

!§8o 

M 

jo*i> 

0  0*0  "S 

cS  O  ^ 

Microhms. 

Ohms. 

Ohms. 

Ohms. 

Ohms. 

Silver   annealed 

1.521 

0.01937 

0.1544 

9.151 

.2214 

Silver  hard  drawn  

1.652 

0.02103 

OJ680 

9!  936 

2415 

Copper  annealed    

1.616 

0.02057 

0.1440 

9.718 

.2064 

Copper  hard  drawn 

l.(52 

0.02104 

0  1469 

9  940 

.2106 

Gold  annealed  

2  081 

0  02650 

0^4080 

12^52 

.5849 

Gold  hard  drawn 

2.118 

0.02697 

0.4150 

12.74 

.5950 

Aluminium,  annealed  

2.945 

0.03751 

0!0757 

17^72 

'l085 

Zinc  pressed  

5  689 

0.07244 

0.4067 

34.22 

.5831 

Platinum,  annealed  

9.158 

0.1166 

1^96 

55  09 

2  810 

Iron   annealed  

9  825 

0.1251 

0.7654 

59.10 

1.097 

Nickel  annealed 

12.60 

0.1604 

1.071 

75.78 

1  535 

Tin  pressed  

13.36 

0.1701 

0^9738 

80^36 

l'396 

Lead  pressed 

19.85 

0.2526 

2.257 

119  39 

3  236 

Antimony,  pressed  

35.90 

0.4571 

816 

3^456 

Bismuth  pressed 

132.7 

1.689 

13^03 

-  798 

18  64 

Mercury,  liquid  
Platinum  silver 

99.74 
24.66 

1.2247 
0.3140 

13.06 
2.959 

578.6 
148.35 

18^72 
4.243 

German  silver,  hard  or  an-  [ 
nealed  \ 

21.17 

0.2635 

1.85 

127.32 

2.652 

Gold  -  silver  alloy,  hard  or  j 
annealed:  two  parts  gold,  V 

10.99 

0.1399 

1.668 

66.10 

2.391 

one  part  silver  ) 

Resistance  of  one  cu- 
bic centimetre  be- 
tween    opposed 
faces,      expressed 
in  microhms. 

Temperature, 
Centigrade. 

Graphite  specimen,  No.  1  
"            No.  2  
"              "            No  3 

2,390 
3,7"80 
41  800 

22° 
22° 
22° 

Gas-retort  carbon  »  
Carbon  in  Bunsen's  battery 

4,280 
67200 

25° 
26  2° 

Tellurium  

212,500 

19.6 

Red  phosphorus  

132  ohms 

20° 

TABLES. 


255 


III.    CONDUCTIVITY   OF   LIQUIDS. 

(Ed.  Becqucrel. — Annales  de  Chimie  et  de  Physique,  June  1846.) 


SUBSTANCES. 

Specific  Weight. 

Temperature, 
Centigrade. 

Conductibility. 

Coefficient  of 
the  increase  of 
conductibility 
for  1°  centigr. 

OBSERVA- 
TIONS. 

Silver  

0° 
9.25 
9.25 
9.25 
13.40 
13.40 
13.40 
13.40 

13.40 
13.00 
13.00 
13.00 

13.00 
14.40 

14.40 
14.40 
12.50 
19.00 
13.10 

15.00 

100,000,000.00 
5.42 
3.47 
2.08 
31.52 
23.08 
17.48 
13.58 

10.35 
8.995 
1C.  208 
17.073 

13.442 

5.77 

7.13 
5.43 
11.20 
88.68 
93.77 

112.01 

0.0286 

0!0223 
0.0263 

Maximum. 
Maximum. 

Sulphate  of  copper,  satu- 
rated   

1.1707 
1.1707 
1.1707 
1.1707 
1.1707 
1.1707 
1.1707 

1.1707 

1.6008 

Sulphate    of    copper,    di- 
luted to  half  

Sulphate   of    copper,    di- 
luted to  quarter 

Chloride  ot   sodium,  satu- 
rated 

Chloride   of     sodium,    di- 
luted to  half    

Chloride    of    sodium,    di- 
luted to  third  
Chloride    of    sodium,   di- 
luted to  quarter  
Bichloride  of  copper,  sat- 
urated and  diluted  with 
five    times   its   bulk   of 
water  

Nitrate    of  copper,  satu- 
rated 

Nitrate  of  copper,  diluted 
to  i 

Nitrate  of  copper,  diluted 
to  half 

Nitrate  of  copper,  diluted 
to  quarter 

Sulphate  of  zinc,  saturated 
Sulphate  of  zinc,  diluted 
to  half  
Sulphate  of   zinc,  diluted 
to  quarter  

1.4410 
1.4410 
1.4410 
1.4410 
1.4410 
1.4410 

1.4410 

Iodide    of    potassium,    30 
gr.  ;  water,  250  gr  
Monohydrate  sulphuric,  20 
gr.  ;  water,  220  gr  

Nitric     acid,    commercial 
(sp  w  1  31) 

Protochloride   of   antimo- 
ny. 30  gr.  ;  water,  120  gr.  ; 
and   hydrochloric   acid, 
100  gr  

This  table  shows  the  maximum  conductibilities  of  the  solutions  of  nitrate  of 
copper  and  sulphate  of  zinc,  but  not  that  of  chloride  of  sodium.  The  maxi- 
mum conductibility  of  this  latter  is  found  in  a  mixture  of  24.4  parts  of  chloride 
for  100  of  water. 


256 


TABLES. 


IV.    LIQUID  RESISTANCES. 

(Table  taken  from  Fleeming  Jenkin.     Calculated  by  Becker.) 
SULPHATE  OF  COPPER. 


Percentage  of 
salt  in  solu- 
tion. 

TEMPERATURE,  CENTIGRADE. 

OBSERVATIONS. 

14° 

16° 

18° 

20° 

24° 

28° 

30° 

8 
12 
16 
20 
24 
28 

45.7 
36.3 
31.2 

28.5 
26.9 
24.7 

43.7 
34.9 
30.0 
27.5 
25.9 
23.4 

41.9 
33.5 

28.9 
26.5 
24.8 
22.1 

40.2 
32.2 
27.9 
25.6 
23.9 
21.0 

37.1 

29.9 
26.1 
24.1 
22.2 
18.8 

34.2 

27.9 
24.6 
22.7 
20.7 
16.9 

32.9 

27.0 
24.0 
22.2 
20.0 
16.0 

Resistance  of  a 
cubic  centimetre 
expressed  in 
ohms. 

SULPHURIC  ACID— DILUTED. 


SPECIFIC 
GRAVITY. 

0° 

40 

8° 

12° 

16° 

20° 

24° 

28° 

1  10 

1.37 

1.17 

1.04 

.925 

.845 

.786 

.737 

.709 

Resistance  of  one 

.20 

1.33 

1.11 

.926 

.792 

.666 

.567 

.486 

.411 

cubic     centi- 

.25 

1.31 

1.09 

.896 

.743 

.624 

.509 

.434 

.358 

metre  to  con- 

.30 

1.36 

1.13 

.94 

.79 

.662 

.561 

.472 

.394 

duction    be- 

.40 
.50 
.60 

1.69 
2.74 

4.82 

1.47 
2.41 
4.16 

1.30 
2.13 
3.62 

1.16 
1.89 
3.11 

1.05 
1.72 
2.75 

.964 
1.61 
2.46 

.896 
1.52 
2.21 

.839 
1.43 
2.02 

tween  opposed 
faces  expressed 
in  ohms. 

.70 

9.41 

7.67 

6.25 

5.12 

4.23 

3.57 

3.07 

2.71 

SULPHATE  OF  ZINC. 


10° 

12° 

14° 
20.2 

16° 
19.2 

18° 

20° 

».. 

22° 
16.3 

24° 
15.6 

96  grammes  in  100  c.c.  ) 
of  solution  f 

22.7 

21.4 

au 

Resistance  of  one 
cubic  centimetre. 

The  same  solution ) 
with  an  equal  vol-  V 
umeof  water ) 


10° 


12° 


14° 


18° 


21.120.319.518.818.1 


17.3 


Expressed  in  ohms. 


2° 
1.94 

4° 

8° 
1.65 

12° 

16° 

20° 

24° 

28° 

Nitric  acid   (sp.    w.  ) 
1  36)                          \ 

1.83 

1.50 

1.39 

1.30 

1.22 

1,18 

Resistance  of  one, 
cubic  centimetre 
in  ohms. 

TABLES. 


257 


DILUTE   SULPHURIC  ACID. 

(Bineau's  Table.) 


go 

I 

TEMPERATURE  =  0°  CENTIG. 

TEMPERATURE  =  15°  CENTIG. 

PIJ 

1 

Monohydrate 
acid  for  100 

A  n  h  y  dride  Monohydrate 
acid  for  100  I    acid  for  100 

Anhydride 
acid  for  IOC 

"S 

*s 

of  the  mix- 

of the  mix- 

of the  mix- 

of the  mix- 

H 

& 

ture. 

ture. 

ture. 

ture. 

0? 

5.0 

.060 

5.1 

4.2 

5.4 

4.5 

10.0 

.075 

10.3 

8.4 

10.9 

8.9 

15.0 

.116 

15.5 

12.7 

16.3 

13.3 

20.0    . 

.161 

21.2 

17.3 

22.4 

18.3 

25.0 

.209 

27.2 

22.2 

28.3 

23.1 

30.0 

.262 

33.6 

27.4 

34.8 

28.4 

33.0 

.296 

37.6 

30.7 

38.9 

31.8 

35.0 

.320 

40.4 

33.0 

41.6 

34.0 

36.0 

.332 

41.7 

34.1 

43.0 

35.1 

37.0 

.345 

43.1 

35.2 

44.3 

39.2 

38.0 

.357 

44.5 

36.3 

45.5 

32.2 

39.0 

.370 

45.9 

37.5 

46.0 

38.3 

40.0 

.383 

47.3 

38.6 

48.4 

39.5 

41.0 

.397 

48.7 

39.7 

49.9 

40.7 

42.0 

.410 

50.0 

40.8 

51.2 

41.8 

43.0 

.424 

51.4 

41.9 

52.5 

42.9 

44.0 

.438 

52.8 

43.1 

54.0 

44.1 

45.0 

.453 

54.3 

44.3 

55.4 

45.2 

46.0 

.468 

55.7 

45.5 

56.9 

46.4 

47.0 

.483 

57.1 

46.6 

58.2 

47.5 

48.0 

.498 

58.5 

47.8 

59.6 

48.7 

49.0 

.514 

60.0 

49.0 

61.1 

50.0 

50.0 

.530 

61.4 

50.1 

62.6 

51.1 

51.0 

.546 

62.9 

51.3 

63.9 

52.2 

52.0 

.563 

64.4 

52.6 

65.4 

53.4 

53.0 

.580 

65.9 

53.8 

66.  S 

54.6 

54.0 

.597 

67.4 

55.0 

68.4 

55.8 

55.0 

.615 

68.9 

56.2 

70.0 

57.1 

56.0 

.634 

70.5 

57.5 

71.6 

58.4 

57.0 

.652 

72.1 

58.8 

73.2 

59.7 

58.0 

.671 

73.6 

60.1 

74.7 

61.0 

59.0 

.691 

75.2 

61.4 

76.3 

62.3 

60.0 

.711 

76.9 

62.8 

78.0 

63.6 

61.0 

.732 

78.6 

64.2 

79.8 

65,.! 

62.0 

.753 

80.4 

65.7 

81.7 

66.7 

63.0 

.774 

82.4 

67.2 

83.9 

68.5 

64.0 

.796 

84.6 

69.0 

86.3 

70.4 

65.0 

.819 

87.4 

71.3 

89.5 

73.0 

65.5 

.830 

89.1 

71.2 

91.8 

749 

65.8 

.as? 

90.4 

73.8 

94.5 

77.1 

66.0 

1.842 

91.3 

74.5 

100.0 

81.6 

66.2 

1.846 

92.5 

75.5 

.... 

66.4 

1.852 

95.0 

77.5 

.... 

66.6 

1.85* 

100.0 

81.6 



258 


TABLES. 


VI.    RESISTANCE   OF  DIFFERENT   LIQUIDS. 


DILUTE  SULPHURIC  ACID  after  SA- 

WELJEV. 

CHLORIDE  OP  SODIUM. 

NITRATE  OP  POTASH. 

(Extract  from  WIEDEMANN.) 

| 

Ha* 

t- 

|§ 

43  qj 

11 

*| 

1 

||s 

1 

**{ 

it 

||| 

if 

1 

Pi* 

s  § 

CO 

I 

iil 

£)  T-< 

III 

'is 

«& 

fi 

H° 

M 

PH 

s 

K~ 

1.003 

0.5 

16.1 

16.01 

25.8758 

0.59852 

18.9167 

0.83271 

1.018 

2.2 

15.2 

5.47 

24.4033 

0.57982  * 

13.7647 

1  .  10G26 

1.053 

7.9 

13.7 

1.884 

20.9787 

0.63840 

10.4840 

1.35099 

1.080 

12.0 

12.8 

1.368 

17.0174 

0.71109 

6.6079 

1.94955 

1.147 

20.8 

13.6 

0.960 

10.4525 

1.03934 

3.3964 

3.32633 

1.190 

26.4 

13.0 

0.871 

6.0957 

1.55599 

1.5452 

6.38318 

1.215 

29.6 

12.3 

0.830 

3.6880 

2.46492 

1.225 

30.9 

13.6 

0.862 

1.7177 

5.56571 

1.252 

34.3 

13.5 

0.874 

1.277 

87.3 

0.930 

*  Minimum. 

1.348 

45.4 

17.9 

0.973 

1.393 
1.492 

50.5 
60.6 

14.5 
13.8 

1.086 
1.549 

1.638 
1.726 

1.827 

73.7 
81.2 
92.7 

14.3 
16.3 
14.3 

2.786 
4.&37 
5.320 

The  above  figures  are  taken  from  a  me- 
moir of   Schmidt  ;    Annales  de  Poggen- 
dorff.    See  Wiedemann,  vol.  i.  p.  324. 
It  is  seen  that  the  maximum  conducti- 

The  above  figures  show  the  max- 
imum conductibility  of  the  mix- 
ture to  be  that  of  29  to  30  parts  of 
the  monohydrate  acid  for  100  of 
water  ;  a  little  different  from  that 
of  the  preceding  table. 


bility  or  the  minimum  resistance  of  the 

sea-salt  solution  corresponds  to  24.4  for 

100  of  water. 
The  figures  correspond  to  the  Jacobi's 

standard  of  resistance,  and  must  be  mul- 
I  tiplied  by  598  X  107  to  be  brought  to  elec- 
I  tro-magnetic  absolute  measurements. 


Experiments  of  Horsford,  1847.     (See  Wiedemann.) 

Chloride  of  potassium,  27. 6  grammes  in  500  grammes  of  water 577,100 

diluted  to  half 1,103,700 

quarter 2,006,500 

Chloride  of  sodium,  27.6  grammes  in  500  grammes  of  water 577,100 

diluted  to  half 1,488,200 

Chloride  of  calcium,  dissolved  (sp.  w.,  1 . 04) 672,560 

Chloride  of  magnesium 672,560 

Chloride  of  zinc 1,092,500 

Experiments  of  Wiedemann  (lS56)from  18°  to  20°  Centigrade. 

SULPHATE-OF-COPPER   SOLUTION. 

31 . 17  grammes  in  one  litre  of  water .    7,805,000 

4,202,000 
3,5i4,000 


62.34 
77.92 
93.51 

124.68 
155.85 
187.02 


3,178,000 
2,567,000 
2.181,000 
1,936,000 


TABLES. 


259 


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260 


TABLES. 


VIII.    ELECTRO-MOTIVE  FORCES. 

(Poggendorff,  1845. — Extract  from  Wiedemann.) 

SINGLE-LIQUID  BATTERIES. 


Zinc  

Daniell  = 
Tin         .   . 

1.000 
0  409 

Tin                    .     ... 

Copper 

0  410 

Zinc 

0  824 

Iron        

Sulphuric  acid  (sp.  w.  —  1  838) 

Copper 

0  417 

Zinc 

[•     diluted  with  49  times  its  weight  -j 

Silver 

1  053 

Zinc 

of  water 

0  339 

Cadmium. 

Iron     .'     .   . 

0  191 

Amalgamated  zinc.. 
Amalgamated  zinc.. 

Iron  
Tin  

0.537 
0  531 

Amalgamated  zinc.. 
Amalgamated  zinc.. 

Nitric  acid  (sp.  w.  =  1.22)  diluted 
with  9  times  its  w'ght  of  water 

Copper  
Platinum  .. 

0.882 
1.495 

Amalgamated  zinc.. 
Amalgamated  zinc.. 
Copper  

Hydrochloric  acid  (sp.  w.  =  1  .  113), 
diluted  with  9  times  its  weight 
of  water  

Copper  
Platinum.  .  . 
Platinum.  .  . 

0.788 
1.537 
0.771 

Silver  
Zinc  . 

Platinum.  .  . 
Iron  

0.620 
1  003 

Zinc              

Potash  in  6  times  its  weight  of 

Silver 

1  198 

Zinc 

water 

Platinum 

1  257 

Zinc 

Antimony  .  . 

0  541 

Zinc 

Carbonate  of  potash 

Iron 

0  832 

Zinc         

( 

Copper  

0  909 

Zinc  

[Carbonate   of   potash,    concen- 
f    trated 

Platinum.  .  . 

1.078 

Iron  
Zinc                   

Choride  of  potassium  

( 

Copper  
Iron 

0.072 
0  476 

Zinc 

Copper 

0  743 

Zinc  

i  Chloride  of  potassium,  concen- 
trated    " 

Platinum.  .  . 

1.346 

Iron  

. 

Copper  

0.260 

TWO-LIQUID  BATTERIES. 


Iron. 

SO3HO-f49HO   by 
weight 

0  461 

Iron. 
Zinc. 

Sulphuric  acid  
Sulphuric   acid  1, 
water  4  

Nitric  acid  
Nitric  acid,  fuming 

Platinum!."." 
Platinum 

1.177 
1  812 

Zinc. 

Sulphuric  acid   1, 
water  4 

"     (sp  w  1  33) 

1  678 

Grove..  .  - 

Zinc. 
Zinc. 
Zinc. 

Zinc. 
Zinc. 
Zinc. 

Sulphuric  acid   1, 
water  12  
Sulphuric  acid    1, 
water  4  
Sulphuric  acid   1, 
water  12  
Sulphate  of  zinc... 
Sea-salt,  NaCl  
Sulphuric  acid   1, 
water  4  

"     (sp.w.1.33) 
"     (sp.w.1.19) 

"     (sp.w.1.19) 
"     (sp.w.1.33) 
'     (sp.w.1.33) 

Sulphate  of  cop- 

Platinum. .  . 
Platinum.  .  . 

Platinum.  .  . 
Platinum.  .  . 
Platinum.  .  . 

Copper 

1.603 
1.558 

1.512 
1.550 
1.765 

1  000 

Zinc. 

Sulphuric  acid    1, 
water  12  

per,     concen--! 
trated  

Copper 

0  906 

Daniell. 

Zinc. 
Zinc. 
Zinc. 
Zinc. 

Sea-salt  1,  water  4  . 

1  Bichromate  of  j 
j        potash  3.       | 

Sulphuric    acid  j 
4,  water  18....  1 

Copper  
Copper  
Carbon  .... 
Platinum.  .  . 

'i'cis 

1.574 
0.977 

TABLES. 


261 


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Nitric  acid 
Nitric  acid 
Chromic  mix 
Sulphate  of  c 
Sulphate  of  c 


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262 


TABLES. 


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TABLES. 


263 


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REMARKS  UPON  THE  PRECEDING  TABLES. 


IT  is  seen  that  the  Daniell  battery  may  be  superior 
or  inferior  to  the  volt,  according  to  the  proportions  of  the 
mixture  of  sulphuric  acid  and  water  in  which  the  zinc  is 
immersed. 

The  conclusion  to  be  drawn  is  that,  for  a  certain  com- 
position of  this  mixture,  the  electro-motive  force  of  the 
Daniell  is  equal  to  the  volt.  Consequently,  except  for 
researches  requiring  great  precision,  the  English  unit 
(volt)  and  the  Daniell  may  be  indifferently  used. 

The  figures  given  by  different  observers  disagree,  as  is 
seen  from  the  tables ;  these  differences  may  arise  from 
various  causes,  of  which  the  principal  is,  no  doubt,  the 
difference  of  composition  of  the  mixture  in  which  the 
zinc  is  immersed.  The  table  shows  that  the  electro-motive 
forces  of  Dani ell's  and  Grove's  battery  vary  with  the  pro- 
portions of  the  mixture  of  sulphuric  acid  and  water.  It 
seems  as  if  there  might  be  made  a  very  interesting  study 
upon  this  question,  searching,  for  instance,  the  conditions 
of  the  maximum  electro-motive  force  of  an  element. 

We  conclude  our  tables  with  secondary  batteries  having 
electrodes  of  platinum  and  of  lead  (Plante).  The  ques- 
tion of  finding  out  the  maximum  force  of  polarization  of 
a  voltameter  has  been  studied  by  several  physicists,  and 
it  does  not  seem  to  have  been  definitely  decided  upon. 
The  figures  which  we  give  are  those  of  Wheatstone,  who 
was  the  first  to  undertake  to  determine  it. 


CONCLUSION. 


IN  the  preceding  chapters  we  have  studied  hydro-electric 
batteries ;  that  is,  apparatus  capable  of  producing  electric 
currents  by  means  of  chemical  energy.  They  are  there- 
fore contrivances  which  transform  chemical  action  into 
electricity. 

Thermo-electric  batteries,  of  which  we  have  not  spoken, 
are  contrivances  wThich  transform  heat  into  electricity. 
They  have  made  very  important  progress  of  late  years, 
and  everything  leads  to  the  belief  that  before  long  they 
will  be  of  great  service  to  industry,  whereas  up  to  this 
time  they  have  only  been  of  interest  to  physicists. 

These  two  kinds  of  apparatus  are  not  the  only  ones  by 
which  electricity  may  be  produced  ;  there  are  to  be  cited 
frictional  electrical  machines,  electrophori,  and  machines 
like  those  of  Holtz. 

But  another  category,  that  of  magneto-electric  machines, 
has  lately  assumed  a  rapidly  increasing  importance.  Enor- 
mous progress  has  been  made,  notably  by  Gramme,  which 
has  led  to  the  construction  of  machines  of  unprecedented 
power. 

These  machines,  frictional  machines,  machines  of  Holtz, 
magneto-electric  machines,  are  all  contrivances  which 
transform  movement  into  electricity,  and  should,  there- 
fore, be  classed  together. 

It  appears  certain  that  all  the  apparatus  producers  of 
electricity  that  will  hereafter  be  invented  will  be  com- 


266  CONCLUSION. 

prised  in  one  of  these  three  classes ;  in  other  words,  it 
does  not  .seem  possible  to  produce  electricity  without  ex- 
pending chemical  energy,  heat,  or  movement,  •  because  en- 
ergy only  presents  itself  under  these  four  forms. 

Hydro-electric  batteries  have  of  late  years  made  less 
progress  than  the  apparatus  of  the  other  two  categories, 
but  they  are  still  open  to  improvement,  and  will  eventually 
make  important  progress. 

First  of  all,  the  exact  nature  of  the  chemical  reactions 
which  take  place  in  these  batteries  must  be  elucidated ;  it 
is  disgraceful  that  at  the  present  time  it  is  not  known  ex- 
actly what  goes  on  in  Grove's  or  Bunsen's  battery. 

The  extremely  small  but  incontestable  variations  in 
the  electro-motive  force  of  even  completely  depolarized 
batteries,  such  as  that  of  Daniell,  must  be  explained. 

The  variations  in  the  internal  resistance  must  be  studied, 
variations  which  are  but  incompletely  explained  by  the 
change  in  the  chemical  composition  of  the  liquids. 

Finally,  new  reactions  among  the  infinite  number  pre- 
sented by  chemistry  must  be  used,  and  above  all  zinc  must 
be  dispensed  with,  which  has  hitherto  thrust  itself,  so  to 
speak,  upon  inventors. 


6,ClIARING  CROSS, 
LONDON,  S.W. 


OVERDUE. 


SEP 


740495 

03 


/ 

UNIVERSITY  OF  CALIFORNIA  LIBRARY 


